Fix #141477: Crash during material selection

Material selection didn't support empty geometries. Geometry list can
have nullptrs, when meshes contain more than 16 materials, but some
materials slots are not actually used in the mesh.

Material selection used to still looped over all the materials and
tried to draw geometry that aren't there.

Regression from !139781

Pull Request: https://projects.blender.org/blender/blender/pulls/141608

source/blender/draw/engines/overlay/overlay_prepass.hh

@@ -280,10 +280,16 @@ class Prepass : Overlay {
     ResourceHandle res_handle = manager.unique_handle(ob_ref);
 
     for (int material_id : geom_list.index_range()) {
+      /* Meshes with more than 16 materials can have nullptr in the geometry list as materials are
+       * not filled for unused materials indices. We should actually use `material_indices_used`
+       * but these are only available for meshes. */
+      if (geom_list[material_id] == nullptr) {
+        continue;
+      }
+
       select::ID select_id = use_material_slot_selection_ ?
                                  res.select_id(ob_ref, (material_id + 1) << 16) :
                                  res.select_id(ob_ref);
-
       if (res.is_selection() && (pass == mesh_ps_)) {
         /* Conservative shader needs expanded draw-call. */
         pass->draw_expand(