check if the welcomeWindow exists, before trying to show in it the bundle that is currenly loading

src/net/java/sip/communicator/plugin/splashscreen/SplashScreenActivator.java

@@ -52,6 +52,8 @@ public void serviceChanged(ServiceEvent evt)
 
     public void bundleChanged(BundleEvent evt)
     {
-        welcomeWindow.setBundle(evt.getBundle().getHeaders().get("Bundle-Name").toString());
+        if(welcomeWindow != null && welcomeWindow.isShowing())
+            welcomeWindow.setBundle(evt.getBundle().getHeaders()
+                .get("Bundle-Name").toString());
     }            
 }