fix for regression bug #203261

Opening a local forwarded message results in a blank Mail window
r/sr=bienvenu, a=sspitzer

mailnews/base/resources/content/messageWindow.js

@@ -296,7 +296,7 @@ function OnLoadMessageWindow()
     if (window.arguments[1])
       gCurrentFolderUri = window.arguments[1];
     else
-      gCurrentFolderUri = folder ? folder.folderURL : null;
+      gCurrentFolderUri = folder ? folder.URI : null;
 
     if (window.arguments[2])
       originalView = window.arguments[2];