arcRotateCamera mesh target & panning bug(?).

Hi guys,

i notised some protential bugs setting a camera.target = mesh / mesh.position; and then attempting to pan,

while in my head it would make sense to update the camera.target on panning and stop following the mesh,

what it does:

camera.target = mesh.position; //panning moves the target mesh around.

camera.target = mesh; //attempting to pan crashes babylon.

I made a PG to show it, clicking 1 or 2  on your keyboard or numpad will set the camera targets described above. and you can then pan by right-clicking.

http://www.babylonjs-playground.com/#1Y5NE6#1

Cheers.