Peculiar behaviors when deleting the offline map

### On WPF:
If you delete the currently-stored offline map, the application will throw an I/O exception like this one:


Clicking 'OK' successfully restarts the app and reveals the offline map is indeed deleted.

However, attempting to take offline a new section of map throws this same exception. The behavior loops and I haven't figured out how to work offline yet because of it.

### On UWP:
If you delete the offline map, the application will crash right away.

The application can be re-launched just fine and reveals the offline map is indeed deleted, but on a few occasions, I've been re-prompted to sign in. Seems the crash may also force signing out the user?

Start by reproducing offline-map deletion separately on WPF and UWP, then inspect the reported I/O exception and crash behavior. Done means deleting the current map does not crash or create a loop, and taking a new map section offline works afterward without unexpectedly signing the user out.

Written by the indexing model from the issue text.