[fixed] UV - vertex / tighten

[micheus]

I think I already saw this kind of message for the wings_drag module before.

Thanks for report it. I'm going to take a look on it soon.
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[EDIT]
Yes. It's already fixed in the next version.

p.s. Hank, I edited your post and removed the Long stack trace. The post got too long and usually it's not helpful - it's better to attach the dump file when necessary.
The most important was you provide a way to reproduce it.