If we call `question_bank_helper::create_default_open_instance` with an
empty `$bankname` parameter, it will currently create a new instance
with no name. This leads to exceptions being thrown when we try to load
the course it belongs to.
This adds some validation to ensure the name being passed is not empty.
Once the issue is resolved, and the bank is created with a proper name,
the course will work as normal.
Mark Johnson
377bce2895