Picking is not reliable while the picking renderer is active

When the picking renderer is active, picking sometimes returns invalid ids. Seems to be caused by a corrupted pickCache, as disabling the pickCache seems to solve the problem.

Steps to reproduce:

• swich to picking Renderer
• add a primitive (e.g. sphere triangle sub.)
• choose edit polylines -> add aew polycircle and move across the mesh
• watch the assertion being triggered if you are in debug build.

Edit: Seems not to appear when intel cards on linux systems are used. However nvidia cards on linux definitley show this problem.