Sandbox crash when lvlX_slots_expended is NaN (easy fix)

[ooshhub]

5e Companion

As per this Roll20 thread, non-numeric values in lvlX_slots_expended will cause the resolveslot() function to crash the API sandbox. The issue is with HTML's handling of number inputs, largely with whitespace as the error is invisible to the user, but the attribute value becomes an empty string.
An easy solution would be to change line 320, the .set() operation, to check for isNaN:
if (!isNaN(spent)) charslot.set({current: Math.max(spent - 1, 0)});