Sudoko throws exception for no glossary selected.

[thepurpleblob]

Create an 'empty' sodoku without selecting a Glossary. An exception is thrown.

Although it's clearly an 'error' it's actually a setup that can legitimately be created through users settings. IMO a proper notice should be created explaining the issue.

The snakes and ladders is nicer if you don't select a quiz category. So, at best, it's inconsistent.