Hotfix: game could quit itself mid-session

• Fixed the game quitting itself during play. A recoverable graphics hiccup
was being treated as fatal — the game would vanish with no warning, and
because it never got a chance to save, any progress since your last save
went with it. It now recovers and carries on.

• The game now keeps a small log file. If something goes wrong, you can
send it to us and we'll actually be able to see what happened:

Windows: %APPDATA%\KeypressExpress\log.txt
macOS: ~/Library/Application Support/KeypressExpress/log.txt