Classes Remain after Unselecting All Classes

While testing against the recently released Block Class 7.x-2.0, it was noticed that classes are still being output in a block when all classes defined by Block Class Select are unselected.

If a block is saved with a class from Block Class Select, then the block is edited and the class is unselected, the class will still remain.

It only happens when no other classes are selected in Block Class Select, or the default textfield provided by Block Class.