Type IEndDragHandler expected DragMeTower3d received. i:0.

Unity 4.6 beta is throwing this exception.

Type IEndDragHandler expected DragMeTower3d received. i:0. Object reference not set to an instance of an object
UnityEngine.EventSystems.EventSystem:Update()


I've been using a modified version of DragMe script to instantiate an object 3D.

and the error happens when I try to destroy the object.
public void OnEndDrag(PointerEventData eventData)

{
PlacementManager.deactivatePlaces();
dragging=false;

if (drag3dTower != null&&PlacementManager.currSelectedTower!=null&&PlacementManager.currSelectedTower.isTaken)
Destroy(drag3dTower);
else if(drag3dTower != null)
{
PlacementManager.currSelectedTower.isTaken=true;
drag3dTower.transform.position= new Vector3(PlacementManager.currSelectedTower.transform.position.x,drag3dTower.transform.position.y,PlacementManager.currSelectedTower.transform.position.z);
//drag3dTower.GetComponent<IAController>().activateAIRIG(true);
}
}

is there any workaround?