EXT-8662 FIXED Crash on renaming incomplete inventory items.

I couldn't reproduce this problem, but from what I've seen in the crash
reporter, this is a very old bug affecting viewers 1.2x and 2.x.
When user tries to rename an incomplete inventory item, viewer crashes.

The fix is to disallow renaming incomplete items.

Reviewed by Seraph at https://codereview.productengine.com/secondlife/r/857/

--HG--
branch : product-engine