change != null to isEmpty

platform/platform-impl/src/com/intellij/notification/impl/actions/NotificationTestAction.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2000-2014 JetBrains s.r.o.
+ * Copyright 2000-2016 JetBrains s.r.o.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -204,7 +204,7 @@ public class NotificationTestAction extends AnAction implements DumbAware {
     public Notification getNotification() {
       if (myNotification == null) {
         Icon icon = null;
-        if (myGroupId != null) {
+        if (!StringUtil.isEmpty(myGroupId)) {
           icon = IconLoader.findIcon(myGroupId);
         }
         if ("!!!St!!!".equals(myTitle)) {