FOOL: Warn (abort?) on startup if the finale isn't available

[dfabulich]

When playing The Fool's Errand for the first time, I dumped it using the Dumper Companion, but I foolishly only dumped The Game.dsk; I didn't dump The Show.dsk.

Actual: I beat the game, and then it crashed, with the error, "ERROR: FoolGame::run: Prologue - Finale program not found!"

Expected: Something should have at least warned me that the game was inevitably going to crash when I won. I think it might even be preferable to abort launching the game if the finale isn't available.

[dfabulich]

The Fool's Errand and the "Fool" game engine aren't available in the issue tracker template yet; I left them blank, but this issue should be updated.