Fix (unreported) misisng handling of XR data object pointer in foreach_id.

Very sadge to see this kind of mistakes still exist in 2023 code...

While in theory this commit could be backported to (LTS) releases, would
rather only do it if/when proven it actually fixes user-facing issues.
Fixing such issues so deep in ID management code can have completely
unexpected side effects.

source/blender/windowmanager/intern/wm.c

@@ -93,6 +93,9 @@ static void window_manager_foreach_id(ID *id, LibraryForeachIDData *data)
       }
     }
   }
+
+  BKE_LIB_FOREACHID_PROCESS_IDSUPER(
+      data, wm->xr.session_settings.base_pose_object, IDWALK_CB_USER_ONE);
 }
 
 static void write_wm_xr_data(BlendWriter *writer, wmXrData *xr_data)