bonding: verify if we still have slaves in bond_3ad_unbind_slave()
bonding: verify if we still have slaves in bond_3ad_unbind_slave()

After commit 1f718f0f4f97145f4072d2d72dcf85069ca7226d ("bonding: populate
neighbour's private on enslave"), we've moved the unlinking of the slave
to the earliest position possible - so that nobody will see an
half-uninited slave.

However, bond_3ad_unbind_slave() relied that, even while removing the last
slave, it is still accessible - via __get_first_agg() (and, eventually,
bond_first_slave()).

Fix that by verifying if the aggregator return is an actual aggregator, but
not NULL.

CC: Jay Vosburgh <9ab50f27d4201db9b28483ba83c48ebafbb2aa17@us.ibm.com>
CC: Andy Gospodarek <e3579b1e47f273529f0f929453e939a68ede9fd1@greyhouse.net>
Signed-off-by: Veaceslav Falico <13e4c2c2c15eff98ad47d02f3ccee2d83dc7015d@redhat.com>
Signed-off-by: David S. Miller <fe08d3c717adf2ae63592e4c9aec6e3e404d8e3e@davemloft.net>

KristFoundation/Programs,KristFoundation/Programs,KristFoundation/Programs,KristFoundation/Programs,KristFoundation/Programs,KristFoundation/Programs