New Den HP scaling and crash hotfix

Hey, a quick small patch:

• Fixes a crucial bug that could cause crashes
• New den HP scaling! So that in the endless mode dens don't outscale mountain's health lol. This is just a first test pass of the new hybrid system. It's possible that dens might be too weak or strong at various stages of the game, so more testing must be done, so as always please report if you have any feedback.