PluginLoader: check if plugin list is empty after filter

721ac978a986de0f322528cd6c6f70389aedf1f7 removed the check if the list
of plugins is empty after filtering on file extension ".js".

Change-Id: I450fbf4cf22d8b8f29d2cf35703620dd963eba70
diff --git a/gerrit-gwtui/src/main/java/com/google/gerrit/client/api/PluginLoader.java b/gerrit-gwtui/src/main/java/com/google/gerrit/client/api/PluginLoader.java
index 845599d..8a479dd 100644
--- a/gerrit-gwtui/src/main/java/com/google/gerrit/client/api/PluginLoader.java
+++ b/gerrit-gwtui/src/main/java/com/google/gerrit/client/api/PluginLoader.java
@@ -40,10 +40,14 @@
       callback.onSuccess(VoidResult.create());
     } else {
       plugins = plugins.stream().filter(p -> p.endsWith(".js")).collect(Collectors.toList());
-      self = new PluginLoader(loadTimeout, callback);
-      self.load(plugins);
-      self.startTimers();
-      self.center();
+      if (plugins.isEmpty()) {
+        callback.onSuccess(VoidResult.create());
+      } else {
+        self = new PluginLoader(loadTimeout, callback);
+        self.load(plugins);
+        self.startTimers();
+        self.center();
+      }
     }
   }