Blender Git Loki

Fix T84416: Vertex color baking checks for UVMap

Since the introduction in rB2221389d6e8e, baking to vertex colors would
still check for the existence of a valid UVMap (as if baking to image
textures).

Now check for vertex colors instead if target is
R_BAKE_TARGET_VERTEX_COLORS.

Maniphest Tasks: T84416

Differential Revision: https://developer.blender.org/D10006