context menu <visible> conditions

What is the correct syntax for <visible> for a context menu addon?

<visible>
[Container.Content(movies) | Container.Content(episodes) | Container.Content(tvshows) | Container.Content(seasons) |
Container.Content(musicvideos)] +
!IsEmpty(Window(10000).Property((ListItem.DBID)”-tmdb”))
</visible>
The IsEmpty…. part is not working.
Assuming a DBID of 1234, I have set the property Window(10000).1234-tmdb to something.
The intention is to only show the item in the context menu if the property for the DBID has been set.
TIA for any insight.