Object Stuck on Screen Even After Target is Gone

I have an image target set, and a 3D object set to appear when the camera recognizes the image target. But when i move the image target off screen, the 3D object doesn’t disappear. Sometimes it gets stuck at the corner of the screen where the image target went off screen, sometimes if I move the image target too fast it gets stuck where the image used to be. See screenshot of stuck object.

How do I get the object to only show up when the image target is visible?

3135219--237693--Screen Shot 2017-07-05 at 2.20.01 PM.png 3135219--237693--Screen Shot 2017-07-05 at 2.20.01 PM.png

Thanks!

Hei could u solved the problem?