Fix T92430: Infinite recursion in some cases in new append code.

Shapekeys, always shapekeys... Since we cannot deal with them as regular
IDs, we need to handle potential recursion cases ourselves here. sigh.

source/blender/windowmanager/intern/wm_files_link.c

@@ -583,8 +583,13 @@ static int foreach_libblock_append_callback(LibraryIDLinkCallbackData *cb_data)
     /* While we do not want to add non-linkable ID (shape keys...) to the list of linked items,
      * unfortunately they can use fully linkable valid IDs too, like actions. Those need to be
      * processed, so we need to recursively deal with them here. */
-    BKE_library_foreach_ID_link(
-        cb_data->bmain, id, foreach_libblock_append_callback, data, IDWALK_NOP);
+    /* NOTE: Since we are by-passing checks in `BKE_library_foreach_ID_link` by manually calling it
+     * recursively, we need to take care of potential recursion cases ourselves (e.g.animdata of
+     * shapekey referencing the shapekey itself). */
+    if (id != cb_data->id_self) {
+      BKE_library_foreach_ID_link(
+          cb_data->bmain, id, foreach_libblock_append_callback, data, IDWALK_NOP);
+    }
     return IDWALK_RET_NOP;
   }