show an alert if we fail to get a document uri (bug 126258) r=cmanske, sr=kin

editor/ui/composer/content/ComposerCommands.js

@@ -1515,7 +1515,10 @@ function Publish(publishData)
 
   gPublishData.docURI = CreateURIFromPublishData(publishData, true);
   if (!gPublishData.docURI)
+  {
+    AlertWithTitle(GetString("Publish"), GetString("PublishFailed"));
     return false;
+  }
 
   if (gPublishData.publishOtherFiles)
     gPublishData.otherFilesURI = CreateURIFromPublishData(publishData, false);