Blender Git Loki

Fix T68826 Eevee: Multi-Mat not working if switching from Solid shading

The correct fix would be to avoid all those hacks but this is needed if
we want to be able to parallelize object vbo extractions.

This is the fixed version of the hack. The issue was that the ibo ranges
were saved before the batch were reset and the IBO was discarded, leading
to a read after free error. All previous reported crash were tested and
are now not reproductible.