ensure parent entrypoint is loaded if direct one is unavailable

app/helpers/webpack_helper.rb

@@ -15,12 +15,18 @@ module WebpackHelper
              end
 
     route = [*controller.controller_path.split('/'), action].compact
-    entrypoint = "pages.#{route.join('.')}"
 
+    until chunks.any? || route.empty?
+      entrypoint = "pages.#{route.join('.')}"
       begin
         chunks = entrypoint_paths(entrypoint, extension: 'js')
       rescue Gitlab::Webpack::Manifest::AssetMissingError
         # no bundle exists for this path
+      end
+      route.pop
+    end
+
+    if chunks.empty?
       chunks = entrypoint_paths("default", extension: 'js')
     end