I'm creating an online game where people log in and then have the list of current players displayed. When the user enters a "room" it dispatches an SFSEvent which includes a Room object with the list of users as User objects in that room. As that event's callback function, I get the list of current users which is an Array, switch the View Stack child index, and then I wrap the user list array in an ArrayList before I assign it to the MXML Spark List component's dataSource. Here's my code:

My Actionscript Code Section (PreGame.as):

private function onRoomJoin(event:SFSEvent):void
{
    const room:Room = this._sfs.getRoomByName(PREGAME_ROOM);

    this.selectedChild = waitingRoom;

    /** I know I should be using event listeners
     *  but this is a temporary fix, otherwise
     *  I keep getting null object errors
     *  do to the li_users list not being
     *  created in time for the dataProvider assignment **/
    setTimeout(function ():void {
        const userList:ArrayList = new ArrayList(room.userList);
        this.li_users.dataProvider = userList;  // This is where the error gets thrown
    },1000);
}

My MXML Code:

<?xml version="1.0" encoding="utf-8"?>
    <mx:ViewStack xmlns:fx="http://ns.adobe.com/mxml/2009" 
        xmlns:s="library://ns.adobe.com/flex/spark" 
        xmlns:mx="library://ns.adobe.com/flex/mx"
        initialize="preGame_initializeHandler(event)"
        >

        <fx:Script source="PreGame.as"/>

        <s:NavigatorContent id="nc_loginScreen">

            /** Login Screen Code **/

        </s:NavigatorContent>

        /** Start of Waiting Room code **/
        <s:NavigatorContent id="waitingRoom">
            <s:Panel id="pn_users"
                     width="400" height="400"
                     title="Users">

                /** This is the List in question **/
                <s:List id="li_users"
                        width="100%" height="100%"/>

            </s:Panel>
        </s:NavigatorContent>
    </mx:ViewStack>

However, I keep getting this error:

TypeError: Error #1010: A term is undefined and has no properties

Any ideas what I'm doing wrong? The arrayList has data, so I know it's not empty/null.