EHN: ext_applicable._make_fallback returns undefined when fallback is undefined

src/core/js/ext_applicable.js

@@ -233,12 +233,15 @@ var ext_applicable = function($, logger, is_in_view_port, load_config, getEntity
    * @return {Creator}
    */
   const _make_fallback_creator = function(fallback) {
+    if (fallback) {
       return {
         id: "_generated_fallback_creator",
         is_applicable: (entity) => true, // always applicable
         create: typeof fallback === "function" ? fallback : (entity) => fallback,
       };
     }
+    return undefined;
+  }
 
   const _make_creator = function (c) {
     return {
@@ -289,7 +292,8 @@ var ext_applicable = function($, logger, is_in_view_port, load_config, getEntity
   const _make_get_container_wrapper = function (get_container_cb, app_name) {
     const _wrapper = function (entity) {
       const container = get_container_cb(entity);
-      if(!$(container).data(app_name)) {
+      const app_done = $(container).data(app_name);
+      if(!app_done) {
         // mark container as used
         $(container).data(app_name, "done");
         return container