EXT-6934 FIXED method LLInventoryObject::rename does not change Name, if...

EXT-6934 FIXED method LLInventoryObject::rename does not change Name, if string is empty after correction.

Problem description:
LLInventoryObject::rename corrects incoming string and remove odd spaces,
for example converts string "    " to empty string "",
as the result empty string can be set as InventoryObject name.

Reviewed by Vadim Savchuk at https://codereview.productengine.com/secondlife/r/505/

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branch : product-engine