Magicka is depleted when using uncastable spells

For example:

• Player has 10 magicka but attempts to cast Chameleon, which costs 15 magicka
• Player cannot cast the spell (animation doesn't play, etc.), but their magicka goes down to zero.

Magicka should not be depleted in this situation.

(RM-1105 from redmine: created on 2014-01-14 by Nicola Bodill, , closed on 2014-01-14 by scrawl .)