Blender Git Loki

Fix T81775: Object Disappears During Texture Painting

Issue was that the `tris_per_mat` are not created when the first batch is drawn
during select operator and then is not created when needed by the workbench pass
since they are not tracked by mesh_buffer_cache_create_requested.

This change will create the `tris_per_mat` just in case they are needed later.
Solution by Cl�ment Foucault

Differential Revision: https://developer.blender.org/D9430