Blender Git Commit Log

Fix T79373: Forbid painting on linked image from 3DView.

As noted by @lichtwerk (thanks), one can have a local object and/or
material using a linked image data-block, this case needs some different
handling to prevent painting on such linked image.

For now, tweak `BKE_paint_proj_mesh_data_check` (eeeek, that name
prefix!) to consider paintslots with linked image as 'non-existing'.