EXT-8727 FIXED Potential fix for a crash in LLAppearanceMgr::updateClothingOrderingInfo.

I couldn't reproduce the problem (it has happened for only two users, both running MacOSX),
but from what I see in the logs, it might have been caused by (or related to) NULL COF items.
I haven't found out how they appear nor what exactly causes the crash, but just for any
case I added a check to make sure we don't try to update wearables ordering info for such items.

Reviewed by Sergey Litovchuk at https://codereview.productengine.com/secondlife/r/876/

--HG--
branch : product-engine