growfs remove ufs/label and can't reset it with tunefs

Hi all,

once run growfs on a partition that had an UFS label, this label is
removed and it's no more possible to re-set it with tunefs.
Here is how to reproduce (tested on 8.3 and 9.0):

mdconfig -a -t malloc -s 10MB
gpart create -s mbr /dev/md0
gpart add -t freebsd -s 5MB /dev/md0
newfs -L THELABEL /dev/md0s1
glabel status | grep THELABEL
=> Label is present, now we resize the slice:
gpart resize -i 1 /dev/md0
glabel status | grep THELABEL
=> Label is still present, now we growfs the slice:
growfs /dev/md0s1
glabel status | grep THELABEL
=> UFS label disapear !
Ok, I will try to re-set it:
tunefs -L THELABEL /dev/md0s1
glabel status | grep THELABEL
=> Still no label !?!

Should I create a PR about this problem ?

Regards,

Olivier