Empty action list for a non-terminal state not handled in player functions

[AdityaDaflapurkar]

@MrDupin, @norvig The player functions in games.py currently throw an error and the execution terminates if at a certain non-terminal game state, the player has no legal moves i.e. the action list is empty. Ideally a player should lose his turn and the game should continue if there are no legal moves. How can this situation be handled?