如何在移动到as3中的下一帧之前删除补间

I have a movieclip which spins. I want it when users drag and drop it to stop spinning and be in it's initial position. I wrote this code but i get error TypeError: Error #1009: Cannot access a property or method of a null object reference. at omoixes10_fla::MainTimeline/EntFrame() when I move to next frame. I can not see what i did wrong. Can you please help me with my code? Do I have to remove tween before I move to next frame? I have a movieclip which spins. I want it when