Nexus Clash

As the title says. When falling below Good MO, a few weird things happen:
- Spells can be cast as normal, while other skills are lost as expected
- All skills appear unpurchased in the Purchase Skills menu. Duplicates cannot be purchased (I tried), but neither can child skills of already-purchased skills (e.g. I had Spell Combat but couldn't buy Battle Magic).

This is fixed on dev. (Note: Inability to purchase child spells while your powers are lost is intentional; there is now an error message that makes that clearer).