This would happen if a tile is found on disk, painting would actually
request that tile (because corresponding uvs were in that range), but
that tile was not added in blenders list of tiles in that Image.
Need to also check tile in `image_quick_test` (regardless of iuser
having passed).
thx @lukasstockner97 for additional input!
Maniphest Tasks: T73110
Differential Revision: https://developer.blender.org/D6578
aee2b754dc