I'm getting and error when importing leads using Eloader. I'm using Round Robin Record Assignment modified using the code from here to work on Leads. I also have a trigger and class from this post to fire off the assignment rule since there is no option for that when importing through Eloader. I'm getting the error below when importing a list. When I manually create leads everything is working fine but when I try and import a list using eloader I get this error. I'm still new to apex so I don't get the problem. Any help?

FATAL_ERROR System.NullPointerException: Attempt to de-reference a null object

FATAL_ERROR Trigger.leadRoundRobin: line 81, column 1

78        for (Integer i : queueIds.keySet())
79        {
80       Assignment_Groups__c[] ags = asgnGroups.get(asgnGroupNameIds.get(i));
81       if (ags.size()>0)
82       {

// leadsRoundRobin.trigger:
 
trigger leadRoundRobin on Lead (before insert, before update) {
 //
    //Check if assignment owner has changed
    //
    Map<Integer,Id> queueIds = new Map<Integer,Id>();   //Trigger index --> Queue ID
    
    Integer idx = 0;
    for (Lead l : Trigger.new)
    {
        if(Trigger.isUpdate) {  
            if(l.OwnerId <> Trigger.oldMap.get(l.id).OwnerId) {
                if (l.TempOwnerId__c == 'SKIP') {
                    Trigger.new[idx].TempOwnerId__c = '';
                } else {
                    queueIds.put(idx, l.OwnerId);
                }
            }           
        }else {
            queueIds.put(idx, l.OwnerId);
        }   
        idx++;
    }
    System.debug('>>>>>queueIds: '+queueIds);
    if (queueIds.isEmpty()) return;
    
    //
    //Find active Assignment Group for Queue
    //
    Map<Integer,Id> asgnGroupNameIds = new Map<Integer,Id>();   //Trigger index --> Assignment_Group_Name ID
    Map<Id,Assignment_Group_Queues__c> asgnGroupQueues = new Map<Id,Assignment_Group_Queues__c>(); //Queue ID --> Assignment Group Queues
    
    for(Assignment_Group_Queues__c[] agq : [SELECT Assignment_Group_Name__c, QueueId__c
                                          FROM Assignment_Group_Queues__c 
                                          WHERE QueueId__c in :queueIds.values()
                                          AND Active__c = 'True'])
    {
        for (Integer i = 0; i < agq.size() ; i++) {
            asgnGroupQueues.put(agq[i].QueueId__c, agq[i]);
        }                                           
    }
    System.debug('>>>>>asgnGroupQueues: '+asgnGroupQueues); 
    if (asgnGroupQueues.isEmpty()) return;
 
    for (Integer i : queueIds.keySet()) {
        Assignment_Group_Queues__c agq = asgnGroupQueues.get(queueIds.get(i));
        
        if (agq <> null) {
            asgnGroupNameIds.put(i, agq.Assignment_Group_Name__c);
        }
        //else no active assignment group queue error
    }
    System.debug('>>>>>asgnGroupNameIds: '+asgnGroupNameIds);
    if (asgnGroupNameIds.isEmpty()) return;
    
    //
    //Determine next valid user in Queue/Assignment Group for round robin
    //User with earliest last assignment date wins.
    //
    Map<Id,Assignment_Groups__c[]> asgnGroups = new Map<Id,Assignment_Groups__c[]>(); // Assignment Group Name ID --> User ID
    for(Assignment_Groups__c[] ags : [SELECT Group_Name__c, User__c, Last_Assignment__c, Millisecond__c 
                                   FROM Assignment_Groups__c 
                                   WHERE Group_Name__c in :asgnGroupNameIds.values() 
                                   AND Active__c = 'True' AND User_Active__c = 'True'
                                   ORDER BY Last_Assignment__c, Millisecond__c])
    {
        if (ags.size()>0) {
            asgnGroups.put(ags[0].Group_Name__c, ags);
        }
    }
    System.debug('>>>>>asgnGroups: '+asgnGroups);   
    if (asgnGroups.isEmpty()) return;
 
    Map<Id,Assignment_Groups__c> updateAssignmentGroups = new Map<Id,Assignment_Groups__c>();
    Map<Id, datetime> latestAGDateTime = new Map<Id,datetime>();
    idx = 0;    
    for (Integer i : queueIds.keySet())
    {
        Assignment_Groups__c[] ags = asgnGroups.get(asgnGroupNameIds.get(i));
        if (ags.size()>0)
        {   
            //Choose next user in line if user ID has already been used but not committed in this trigger batch 
            Assignment_Groups__c ag = ags[math.mod(idx, ags.size())];
                
            //Assign User to Lead as the new owner
            System.debug('>>>>>Owner changed for Lead ' + Trigger.new[i].Id + ' from '+Trigger.new[i].OwnerId+' to '+ ag.User__c);
            Trigger.new[i].OwnerId = ag.User__c;    
            Trigger.new[i].TempOwnerId__c = '';  // don't assign back in an endless loop
 
            //Set last assignment datetime
            datetime now = datetime.now();
            ag.Last_Assignment__c = now;
            ag.Millisecond__c = now.millisecondGMT();
            
            //update only latest Assignment Groups per ID
            if (latestAGDateTime.containsKey(ag.id)) {
                if(latestAGDateTime.get(ag.id) < now) {
                    updateAssignmentGroups.put(ag.id, ag);
                    latestAGDateTime.put(ag.id, now);
                }
            } else {
                updateAssignmentGroups.put(ag.id, ag);
                latestAGDateTime.put(ag.id,now);
            }
            
            idx++;
        }
    }
    //Map --> List/Array for DML update
    List<Assignment_Groups__c> updateAG = new List<Assignment_Groups__c>();
    for (Id agId : updateAssignmentGroups.keySet()) {
        updateAG.add(updateAssignmentGroups.get(agId));
    }
 
    System.debug('>>>>>Update Assignment Groups: '+updateAG);   
    
    //
    //Update last assignment for Assignment Group in batch
    //
    if (updateAG.size()>0) {
        try {
            update updateAG;
        } catch (Exception e){
            for (Integer i : queueIds.keySet())
            {
                Trigger.new[i].addError('ERROR: Could not update Assignment Group records ' + ' DETAIL: '+e.getMessage());  
            }
        }
    }
}