Fix T67999: calling Mesh.materials.clear() crashes Blender

The `BKE_material_pop_id()` and `BKE_material_clear_id()` functions had
a parameter `update_data` that, when `false`, would cause the mesh polys
to keep their material index, even when the indexed material slots were
removed. This behaviour was never used in the C code and not supported
by the drawing code, making polygons disappear and causing crashes. The
Python binding in RNA, however, defaulted to `update_data=False`.

This commit removes the `update_data` parameter altogether, and makes
the functions always fix up the material indices.

Reviewed by: mont29, brecht

1 files changed, 2 insertions, 2 deletions

diff --git a/source/blender/editors/mesh/editmesh_tools.c b/source/blender/editors/mesh/editmesh_tools.c
index f57e8141f27..4e58fee61a2 100644
--- a/source/blender/editors/mesh/editmesh_tools.c
+++ b/source/blender/editors/mesh/editmesh_tools.c
@@ -4040,7 +4040,7 @@ static void mesh_separate_material_assign_mat_nr(Main *bmain, Object *ob, const
       ma_obdata = NULL;
     }
 
-    BKE_material_clear_id(bmain, obdata, true);
+    BKE_material_clear_id(bmain, obdata);
     BKE_material_resize_object(bmain, ob, 1, true);
     BKE_material_resize_id(bmain, obdata, 1, true);
 
@@ -4051,7 +4051,7 @@ static void mesh_separate_material_assign_mat_nr(Main *bmain, Object *ob, const
     id_us_plus((ID *)ma_obdata);
   }
   else {
-    BKE_material_clear_id(bmain, obdata, true);
+    BKE_material_clear_id(bmain, obdata);
     BKE_material_resize_object(bmain, ob, 0, true);
     BKE_material_resize_id(bmain, obdata, 0, true);
   }