Let me know if that doesn't answer your question.
Where's the answer? Maybe I'm blind since they've changed this website format...again. But I don't see it.
Seems like answers are getting lost when old posts are getting ported over.
The answer can be found in the help. For example, in this topic:
The brief answer is, when the string is empty, you can tell it to use any user-defined default text (or just make it blank; not sure if it would need a blank space as a sort of place holder or if it can be totally empty) by doing something like this (adjusted for your particular case, of course):
<dyn type="page" property="PageName_NW" emptyStr=""/>