[FIXED] Damage Calc Stat Modifications Produce NaN Errors in Some Situations

This may or may not be fixed with some recent changes, but I want to make sure I have it here.

I was not able to reproduce this one if anyone else can figure it out. Someone on reddit reported. Thanks!

Edit: This appears to happen when people delete the buffs/debuffs instead of setting them to zero.

Bonus/Penalty fields should no longer allow you to leave them blank, and revert to 0. Also do not allow negative values.