Fix T80238: Crash adding properties to material node-trees

The localized node-tree was freeing the materials ID properties twice.

This matches how animation data behaves, setting to NULL after freeing.

source/blender/blenkernel/intern/lib_id_delete.c

@@ -56,10 +56,12 @@ void BKE_libblock_free_data(ID *id, const bool do_id_user)
   if (id->properties) {
     IDP_FreePropertyContent_ex(id->properties, do_id_user);
     MEM_freeN(id->properties);
+    id->properties = NULL;
   }
 
   if (id->override_library) {
     BKE_lib_override_library_free(&id->override_library, do_id_user);
+    id->override_library = NULL;
   }
 
   BKE_animdata_free(id, do_id_user);