A pox on ye, ladders! (i.e. another bug fixed!)

So, it turns out - thanks to discovery by my good friend @retrotap (see YouTube for his channel), that level 15 - the last level dagnammit! - had a bug, where you could move down a ladder where a collectible was located at the bottom, and the player would erase that item without collectiing it (breaking the level), i.e. where I'm standing in the picture below:

On the last level at that! How frustrating!!

I've added a fix (in V7), and it now seems to work fine. But along with the other check I added for the EXIT in an earlier release, this really has slowed down the ladder descent noticeably. It's tolerable, but I think it means I may assemblify (that's a word, I swear) the ladder movement code soon to solve that.

In the meantime though, at least you can now finish the game properly!