[Bf-python] Fixing [ #4834 ] getVertsFromGroup bugs (Mesh and NMesh modules)

[Roland Hess]

http://projects.blender.org/tracker/index.php?func=detail&aid=4834&group_id=9&atid=125

Since I'm a committer now (woohoo!), I was looking through the tracker 
for bugs to fix and ran across this one.

It looks like the reporter found a real bug, and that the function 
doesn't work as advertised in the docs.

The relevant function appears to throw an exception as soon as it 
encounters an out-of-group vert, as opposed to just culling the list and 
returning the final result. The way it's written, it looks to me like 
any out-of-group vert will prevent the return of the list.

Pretty simple to fix... just a removal of the check in question, but I 
didn't want to step on anyone's toes. All it would need would be a final 
check to ensure that there is at least one element left in the list to 
return, otherwise I'd think it ought to return None.

Ken, if you're cool with that, can I fix and commit?

Roland Hess
harkyman