Trying to do a poll with only one option fails gracefully. Example: What kind of book did you read last? [poll]{a book}

Modifying the number of periods modifies the number of options available:

|poll:True............False|

One period is well-defined: Nope. |poll:True.False| throws an "invalid poll type" error.

What about leaving off one of the names? |poll:True...| throws an "invalid poll type" error as well.