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, 3 deletions

diff --git a/source/blender/blenkernel/BKE_material.h b/source/blender/blenkernel/BKE_material.h
index 5bb69c7166e..44a8f98e994 100644
--- a/source/blender/blenkernel/BKE_material.h
+++ b/source/blender/blenkernel/BKE_material.h
@@ -104,9 +104,8 @@ void BKE_material_append_id(struct Main *bmain, struct ID *id, struct Material *
 struct Material *BKE_material_pop_id(struct Main *bmain,
                                      struct ID *id,
                                      /* index is an int because of RNA. */
-                                     int index,
-                                     bool update_data);
-void BKE_material_clear_id(struct Main *bmain, struct ID *id, bool update_data);
+                                     int index);
+void BKE_material_clear_id(struct Main *bmain, struct ID *id);
 /* rendering */
 
 void ramp_blend(int type, float r_col[3], const float fac, const float col[3]);