Bugfix: don't invalidate ItemModContainer's availableSlots - Also restricted access to availableItems to prevent future accidents and make it easier to reason about list's lifetime. This is my bug - Pooling resets available slots on ItemContainer, so if they're shared by ref - original source gets nuked. Tests: got ak47 with ext mag, dropped it, it despawned, spawned new one, tried to put rock into gear slots - it got rejected