[PATCH,HURD] sendto: do not crash when addr is NULL

[Roland McGrath]

> Hm ok, I saw other cases of shadowing by internal subroutines, and 
> assumed it was okay (since inside them you want to refer to the local 
> "err" instead of the outermost one.

It's not the worst thing ever, and we don't compile with -Wshadow.
But shadowing is usually a good thing to avoid just to make reading
the code easier to follow.


Thanks,
Roland