Windows 7 64 + Nvidia GTX560 + Official 2.69
Linux 32 (Ubuntu) + Intel 945GM + Official 2.69
I discovered this while doing python scripting. In some cases I didn't expect, my script ended up creating an empty Shader Node group (having "missing data block"). Seems this is not a problem but it crashes when having the material with that empty group in "Material" shading mode only.
Steps to reproduce the issue:
*Open the attached blend file, and change viewport shading mode to "material". Blender crashes. No log seems to be output in Windows tmp directory.
*The python code in the blend file is the one that generates the corrupted material.