Some older Asttribanks had an empty label string. They should be ignored
when testing for a duplicate label at device probe time.
While we're at it, reduce panic level in the notice.
Signed-off-by: Tzafrir Cohen <tzafrir.cohen@xorcom.com>
git-svn-id: http://svn.asterisk.org/svn/dahdi/linux/branches/2.4@9926 a0bf4364-ded3-4de4-8d8a-66a801d63aff