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

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>
Cc: stable@vger.kernel.org #2.6.11+
Signed-off-by: David S. Miller <davem@davemloft.net>

net/rose/af_rose.c

@@ -192,6 +192,7 @@ static void rose_kill_by_device(struct net_device *dev)
 
 		if (rose->device == dev) {
 			rose_disconnect(s, ENETUNREACH, ROSE_OUT_OF_ORDER, 0);
+			if (rose->neighbour)
 				rose->neighbour->use--;
 			rose->device = NULL;
 		}