BUG: #3438 Avoid hang when saving due to non-visible widget grab

If the OpenGL context of the window is not correctly initialized,
then VTK cannot get a copy of the pixels and goes into an
infinite loop checking the GL error.  This CTK version includes
a patch from Andras avoids this problem.

git-svn-id: http://svn.slicer.org/Slicer4/trunk@22605 3bd1e089-480b-0410-8dfb-8563597acbee