Referring to an undefined ExactlyOne Property throws an Unexpected Error

(Bug, Closed -> Fixed, Priority: High, Test Status: No automated tests yet , Reported By Bad Link: Thing 3y284of not found, )

Summary: Create an ExactlyOne Text Property. (Although I suspect this happens regardless of Type.) Create a page that shows that Property, but doesn't actually define it. (That is, the syntax tries to access the Property.) An Unexpected Error shows up.

Justin: IMO, this situation is an error, and should show a warning of some sort -- otherwise, innocent typos will simply be hidden. But there needs to be an easy way to say "show this Property iff it is defined".

For now, though, I'm going with the straightforward solution, which is to get rid of the inappropriate error. (Giving the error in only the correct situations is going to take a lot of thought and careful design, since it is conceptually legal.)