I am designing a c++ program, somewhere in the program i need to detect if there is a blank(empty token) next to the token used know eg.

if(token1==start)
{   
   token2=strtok(NULL," ");
   if(token2==NULL)
   {LCCTR=0;}
   else 
   {LCCTR=atoi(token2);}

so in the previous peice token1 is pointing to start , and i want to check if there is anumber next to the start , so I used token2=strtok(NULL," ") to point to the next token but unfortunattly the strtok function cannot detect empty spaces so it gives me an error at run time"INVALID NULL POINTER" how can i fix it or is there another function to use to detect empty spaces

#include <iostream>
#include<string>        
#include<map>
#include<iomanip>
#include<fstream>
#include<ctype.h>



using namespace std;
const int MAX=300;

int LCCTR;
int START(char* token1);
char* PASS1(char*token1);

void tokinizer()
{
   ifstream in;                 
   ofstream out;                

   char oneline[MAX];           
   in.open("infile.txt");       
   out.open("outfile.txt");


if(in.is_open())        
   {
       char *token1;
       in.getline(oneline,MAX); 
       token1 = strtok(oneline," \t");
       START (token1);
        //cout<<'\t';

 while(token1!=NULL)
  { 

            //PASS1(token1);
            //cout<<token1<<" ";


            token1=strtok(NULL," \t");

            if(NULL==token1)
            {//cout<<endl;
            //cout<<LCCTR<<'\t';
            in.getline(oneline,MAX);
            token1 = strtok(oneline," \t");
            }

    }
 }
   in.close();
   out.close();

}
int START(char* token1)
{
    string start("START");
    char*token2;
    if(token1 != start)
    {LCCTR=0;}

    else if(token1==start)
    {   
        token2=strchr(token1+2,' ');
        cout<<token2;
        if(token2==NULL)
        {LCCTR=0;}
        else 
       {LCCTR=atoi(token2);
        if(atoi(token2)>9999||atoi(token2)<0){cout<<"IVALID STARTING ADDRESS"<<endl;exit(1);}
        }   
    }
    return LCCTR;

}
char* PASS1 (char*token1)
{       
    map<string,int> operations;
    map<string,int>symtable;
    map<string,int>::iterator it;
    pair<map<string,int>::iterator,bool> ret;
    char*token3=NULL;
    char*token2=NULL;

    string test;
    string comp(" ");
    string start("START");
    string word("WORD");
    string byte("BYTE");
    string resb("RESB");
    string resw("RESW");
    string end("END");

        operations["ADD"] = 18;
        operations["AND"] = 40;
        operations["COMP"] = 28;
        operations["DIV"] = 24;
        operations["J"] = 0X3c;
        operations["JEQ"] =30;
        operations["JGT"] =34;
        operations["JLT"] =38;
        operations["JSUB"] =48;
        operations["LDA"] =00;
        operations["LDCH"] =50;
        operations["LDL"] =55;
        operations["LDX"] =04;
        operations["MUL"] =20;
        operations["OR"] =44;
        operations["RD"] =0xd8;
        operations["RSUB"] =0x4c;
        operations["STA"] =0x0c;
        operations["STCH"] =54;
        operations["STL"] =14;
        operations["STSW"] =0xe8;
        operations["STX"] =10;
        operations["SUB"] =0x1c;
        operations["TD"] =0xe0;
        operations["TIX"] =0x2c;
        operations["WD"] =0xdc;



        if(operations.find("ADD")->first==token1)
        {   token2=strtok(NULL," ");
            //test=token2;
            cout<<token2;
            //if(test.empty()){cout<<"MISSING OPERAND"<<endl;exit(1);}
            //else{LCCTR=LCCTR+3;}
        }
        /*else if(operations.find("AND")->first==token1)
        {   token2=strtok(NULL," ");
            test=token2;
            if(test.empty()){cout<<"MISSING OPERAND"<<endl;exit(1);}
            else{LCCTR=LCCTR+3;}
        }
        else if(operations.find("COMP")->first==token1)
        {   token2=token1+5;
            test=token2;
            if(test.empty()){cout<<"MISSING OPERAND"<<endl;exit(1);}
            else{LCCTR=LCCTR+3;}
        }
        else if(operations.find("DIV")->first==token1)
        {   token2=token1+4;
            test=token2;
            if(test.empty()){cout<<"MISSING OPERAND"<<endl;exit(1);}
            else{LCCTR=LCCTR+3;}
        }
        else if(operations.find("J")->first==token1)
        {   token2=token1+2;
            test=token2;
            if(test.empty()){cout<<"MISSING OPERAND"<<endl;exit(1);}
            else{LCCTR=LCCTR+3;}
        }
        else if(operations.find("JEQ")->first==token1)
        {   token2=token1+5;
            test=token2;
            if(test.empty()){cout<<"MISSING OPERAND"<<endl;exit(1);}
            else{LCCTR=LCCTR+3;}
        }
        else if(operations.find("JGT")->first==token1)
        {   token2=strtok(NULL," ");
            test=token2;
            if(test.empty()){cout<<"MISSING OPERAND"<<endl;exit(1);}
            else{LCCTR=LCCTR+3;}
        }
        else if(operations.find("JLT")->first==token1)
        {   token2=token1+6;
            test=token2;
            if(test.empty()){cout<<"MISSING OPERAND"<<endl;exit(1);}
            else{LCCTR=LCCTR+3;}
        }
        else if(operations.find("JSUB")->first==token1)
        {   token2=token1+6;
            test=token2;
            if(test.empty()){cout<<"MISSING OPERAND"<<endl;exit(1);}
            else{LCCTR=LCCTR+3;}
        }
        else if(operations.find("LDA")->first==token1)
        {   token2=token1+6;
            test=token2;
            if(test.empty()){cout<<"MISSING OPERAND"<<endl;exit(1);}
            else{LCCTR=LCCTR+3;}
        }
        else if(operations.find("LDCH")->first==token1)
        {   token2=token1+6;
            test=token2;
            if(test.empty()){cout<<"MISSING OPERAND"<<endl;exit(1);}
            else{LCCTR=LCCTR+3;}
        }
        else if(operations.find("LDL")->first==token1)
        {   token2=token1+6;
            test=token2;
            if(test.empty()){cout<<"MISSING OPERAND"<<endl;exit(1);}
            else{LCCTR=LCCTR+3;}
        }
        else if(operations.find("LDX")->first==token1)
        {   token2=token1+6;
            test=token2;
            if(test.empty()){cout<<"MISSING OPERAND"<<endl;exit(1);}
            else{LCCTR=LCCTR+3;}
        }
        else if(operations.find("MUL")->first==token1)
        {   token2=token1+6;
            test=token2;
            if(test.empty()){cout<<"MISSING OPERAND"<<endl;exit(1);}
            else{LCCTR=LCCTR+3;}
        }
        else if(operations.find("OR")->first==token1)
        {   token2=token1+6;
            test=token2;
            if(test.empty()){cout<<"MISSING OPERAND"<<endl;exit(1);}
            else{LCCTR=LCCTR+3;}
        }
        else if(operations.find("RD")->first==token1)
        {   token2=token1+6;
            test=token2;
            if(test.empty()){cout<<"MISSING OPERAND"<<endl;exit(1);}
            else{LCCTR=LCCTR+3;}
        }
        else if(operations.find("RSUB")->first==token1)
        {   token2=token1+6;
            test=token2;
            if(test.empty()){cout<<"MISSING OPERAND"<<endl;exit(1);}
            else{LCCTR=LCCTR+3;}
        }
        else if(operations.find("STA")->first==token1)
        {   token2=token1+6;
            test=token2;
            if(test.empty()){cout<<"MISSING OPERAND"<<endl;exit(1);}
            else{LCCTR=LCCTR+3;}
        }
        else if(operations.find("STCH")->first==token1)
        {   token2=token1+6;
            test=token2;
            if(test.empty()){cout<<"MISSING OPERAND"<<endl;exit(1);}
            else{LCCTR=LCCTR+3;}
        }
        else if(operations.find("STL")->first==token1)
        {   token2=token1+6;
            test=token2;
            if(test.empty()){cout<<"MISSING OPERAND"<<endl;exit(1);}
            else{LCCTR=LCCTR+3;}
        }
        else if(operations.find("STSW")->first==token1)
        {   token2=token1+6;
            test=token2;
            if(test.empty()){cout<<"MISSING OPERAND"<<endl;exit(1);}
            else{LCCTR=LCCTR+3;}
        }
        else if(operations.find("STX")->first==token1)
        {   token2=token1+6;
            test=token2;
            if(test.empty()){cout<<"MISSING OPERAND"<<endl;exit(1);}
            else{LCCTR=LCCTR+3;}
        }
        else if(operations.find("SUB")->first==token1)
        {   token2=token1+6;
            test=token2;
            if(test.empty()){cout<<"MISSING OPERAND"<<endl;exit(1);}
            else{LCCTR=LCCTR+3;}
        }
        else if(operations.find("TD")->first==token1)
        {   token2=token1+6;
            test=token2;
            if(test.empty()){cout<<"MISSING OPERAND"<<endl;exit(1);}
            else{LCCTR=LCCTR+3;}
        }
        else if(operations.find("TIX")->first==token1)
        {   token2=token1+6;
            test=token2;
            if(test.empty()){cout<<"MISSING OPERAND"<<endl;exit(1);}
            else{LCCTR=LCCTR+3;}
        }
        else if(operations.find("WD")->first==token1)
        {   token2=token1+6;
            test=token2;
            if(test.empty()){cout<<"MISSING OPERAND"<<endl;exit(1);}
            else{LCCTR=LCCTR+3;}
        }*/

        //else if(


         if(word==token1)
        {LCCTR=LCCTR+3;}

        else if(byte==token1)
        {string test;
        token2=token1+7;
        test=token2;
            if(test[0]=='C')
            {token3=token1+10;
            test=token3;
            if(test.length()>15)
            {cout<<"ERROR"<<endl;
            exit(1);}
            }
            else if(test[0]=='X')
            {token3=token1+10;
            test=token3;
            if(test.length()>14)
            {cout<<"ERROR"<<endl;
            exit(1);}
            }
            LCCTR=LCCTR+test.length();
        }

        else if(resb==token1)
        {token3=token1+5;
        LCCTR=LCCTR+atoi(token3);}

        else if(resw==token1)
        {token3=token1+5;
        LCCTR=LCCTR+3*atoi(token3);}

        else if(end==token1)
        {exit(1);}



    /*else
    {   
        test=token1;
        int last=test.length();
        if(token1==start||test[0]=='C'||test[0]=='X'||ispunct(test[last])||isdigit(test[0])||isdigit(test[1])||isdigit(test[2])||isdigit(test[3])){}
        else    {
                token2=strtok(NULL," ");
                //test=token2;
                cout<<token2;
                if(token2!=NULL)
                {
                    symtable.insert( pair<string,int>(token1,LCCTR));
                    for(it=symtable.begin() ;it!=symtable.end() ;++it)
                        {/*cout<<"symbol: "<<it->first<<"      LCCTR: "<<it->second<<endl;}
                }
                else{}
        }
        }*/




return token3;

}
int main()
{
   tokinizer();
   return 0;
}