NET: ROSE: Don't dereference NULL neighbour pointer.

commit d496f7842aada20c61e6044b3395383fa972872c upstream.

A ROSE socket doesn't necessarily always have a neighbour pointer so check
if the neighbour pointer is valid before dereferencing it.

Signed-off-by: Ralf Baechle <ralf@linux-mips.org>
Tested-by: Bernard Pidoux <f6bvp@free.fr>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>

diff --cc net/rose/af_rose.c
Simple merge