Fix a crashing bug in checkmate recognition.
Merge branch 'master' of github.com:haldean/chess
Merge branch 'master' of github.com:haldean/chess
Merge branch 'master' of github.com:haldean/chess
Merge branch 'master' of github.com:haldean/chess
Merge branch 'master' of github.com:haldean/chess
Merge branch 'master' of github.com:haldean/chess
Merge branch 'master' of github.com:haldean/chess
Merge branch 'master' of github.com:haldean/chess
More stats worker fixes.