Patch for crash on closing

[Cyrille Berger]

Hi,

On Friday 23 October 2009, Sven Langkamp wrote:
> Can you have a look at it?

I disagree with the removal of the Q_ASSERT(!d->ownedByRegistry);
It's there for a reason. So we can either add an other boolean, replaced 
ownedByRegistry by an enum or use a permanent color space in the cache, which 
would remove the need to call colorSpaceIsDestroyed.
-- 
Cyrille Berger