Fix #107913: Creation of liboverrides of Scenes should not be allowed.

It was still possible to create liboverrides of Scene IDs from the
Outliner.

Scenes are currently not officially supported, RNA API allows to create
them for experimental purposes, but UI should not.

source/blender/editors/space_outliner/outliner_tools.cc

@@ -1043,6 +1043,14 @@ static void id_override_library_create_hierarchy_pre_process_fn(bContext *C,
     return;
   }
 
+  if (!ID_IS_OVERRIDABLE_LIBRARY_HIERARCHY(id_root_reference)) {
+    BKE_reportf(reports,
+                RPT_WARNING,
+                "Could not create library override from data-block '%s', as it is not overridable",
+                id_root_reference->name);
+    return;
+  }
+
   BLI_assert(do_hierarchy);
   UNUSED_VARS_NDEBUG(do_hierarchy);