[flexcoders] Getting NULL Object Reference while deleting last element of the list

[anuj181]

Hi Guys
I am trying to implement the delete entries of the list box. The code
works fine till the last entry, when i am trying to delete the last
item after selection it is throwing error TypeError: Error #1009:
Cannot access a property or method of a null object reference.
I have seen this error so many times but I am not sure how will i fix
this in the following code. Please help me in fixing this error
Thanks
Anuj

/*CODE*/

<mx:Button x="322" y="237" label="Add" id="_addButton"
click="addToAssociatedDevices(event)"/>

  private function addToAssociatedDevices(evt:MouseEvent):void
            {  
                var _addDevicesLen:int=devicesInList.length;
                var _addToAssociatedDevicesArr:Array;
                
                
                for(var i:*=0;i<_addDevicesLen-1;i++)
                {
                        _addToAssociatedDevicesArr=nvrsInPoolList.selectedItems;
                        
                                                         
                }
                if((_addToAssociatedDevicesArr is
Array)&&(_addToAssociatedDevicesArr!=null))
                {
                        var removeIndex:int = 0;
                        for each (var addItemVal:* in 
_addToAssociatedDevicesArr) 
                        {
                                if(addItemVal!=null)
                                {
                                
IList(camerasInPoolList.dataProvider).addItem(addItemVal as Object);
                                //Adds a device to the Add To Camera Pool list
                                        arrAddToPool.push(addItemVal);  
                                        //Removes a device from the Remove From 
Pool list
                                                removeIndex = 
arrRemoveFromPool.indexOf(addItemVal);
                                                if(removeIndex > -1) {
                                                        
arrRemoveFromPool.splice(removeIndex,1);
                                                }   
                                }
                        }
                                                
                }
                        for(var t:*=0;t<_addToAssociatedDevicesArr.length;t++)
                        {  
                                if(nvrsInPoolList!=null)
                                {                                               
        
                                
IList(nvrsInPoolList.dataProvider).removeItemAt(nvrsInPoolList.selectedIndex);
                                }       
                        }               
            }