[sldev] Fix for VWR-12827 ( LLVertexBuffer::setupVertexBuffer crash)

[Philippe Bossut (Merov Linden)]

Hi there,

We discussed this issue with devs today and I put together a patch  
that can be applied against the projects/http-texture code. It's  
attached to the PJIRA:
	https://jira.secondlife.com/browse/VWR-12827

Definitely fixed my repro cases. Anyone to apply and test to see if  
that solves the various repro cases people have been signaling?

Cheers,
- Merov