bonding: fix NULL pointer deref in startup processing

	Fix the "are we creating a duplicate" check to not compare
the name if the name is NULL (meaning that the system should select
a name).  Bug reported by Benny Amorsen <benny+usenet@amorsen.dk>.

Signed-off-by: Jay Vosburgh <fubar@us.ibm.com>
Signed-off-by: Jeff Garzik <jeff@garzik.org>
Signed-off-by: David S. Miller <davem@davemloft.net>