Fixed display of 'undefined' instead of empty string in Publish Progress dialog, b=138040, r=brade, sr=kin

editor/ui/dialogs/content/EditorPublishProgress.js

@@ -28,7 +28,7 @@ var gTotalFileCount = 0;
 var gSucceededCount = 0;
 var gFinishedCount = 0;
 var gFinished = false;
-var gFinalMessage;
+var gFinalMessage="";
 var gTimerID;
 
 function Startup()