We'd better not nlmsg_free on a pointer containing an undefined value
(and without having anything allocated).

Spotted by the Coverity checker.
Signed-off-by: NAdrian Bunk <bunk@kernel.org>
Acked-by: NBalbir Singh <balbir@linux.vnet.ibm>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>