Alert shown on rematch when "auto-enable board setup" is enabled

[herzbube]

Steps to reproduce:

• Start new game with a human player being the first to move
• Play a move
• Enable the user preference "auto-enable board setup"
• Start a new game using the "rematch" menu entry

Expected: A new game is started, the app enters board setup mode, no alert is displayed.

Actual: A new game is started, the app does not enter board setup mode, an alert with title "Board setup mode canceled" is displayed.