romario333/opensudoku — pull request #6 by ahgilbert (2012-12-03 04:34:19+00:00)
Title: Allow "Set Checkpoint" on an empty command stack

I have added a NoOpCommand subclass of AbstractCommand. If a user attempts to set a checkpoint on an empty command stack (for example, when coming back to a partially completed puzzle after rebooting the device) a NoOpCommand is pushed to the command stack before setCheckpoint(true) is called. The NoOpCommand has no other behaviors.