[BUG][PLAYER] Possible to get to title screen in playtest mode

[namida]

1. Playtest a level that has a preview and/or postview text
2. Get to the preview / postview text screen
3. Press Esc

You are now on the main menu screen.

This does not happen if you press Esc on the main preview or postview screens; they exit correctly. The code that detects playtest mode and terminates rather than returning to main menu simply needs to be copied to GameTextScreen.

Or, even better: When in playtest mode, change all attempts to load the menu screen to instead exit.

[namida]

Fixed in commit E3E6DAD.