Blender Git Loki

Fix #33371: blender freezing in material draw mode.

When FBO failed in a particular way it could cause the opengl draw buffer to be
set wrong, effectively disabling all opengl drawing. The FBO error was caused
by cycles GLSL materials with no nodes that would still use blender internal
materials, which caused issues with lamp shadow buffers FBO.

This also fixes a GLSL refresh issue when switching render engines.