Bonus Spells Casting Bug

[Glim]

When you memorize spell in the extra slots you receive from a magically enhanced stat score, once that stat score wears off or, if due to an item, is removed, the spell is gone from your memorized list. This is normal.

But, if you have the spell memorized in your non-bonus slots, and you try to cast a spell after you have lost the spell in your bonus slot, it gives the message "You currently do not have enough power to cast <spell>".

Seems that it should default to spells you have access to first before the bonus ones.