Show error when trying to save in read-only mode

We already correctly show the read only error if the user tries
to load VE which the database is locked, but if the database gets
locked after they've loaded VE, we also need to show the error
when they try to save.

Bug: 51636
Change-Id: I7a56f1b4387e7ea594a2a7f939c81626c9eee834
Merge "Show error when trying to save in read-only mode"