netlabel: Compiler warning and NULL pointer dereference fix

Fix the two compiler warnings show below.  Thanks to Geert Uytterhoeven for
finding and reporting the problem.

 net/netlabel/netlabel_unlabeled.c:567: warning: 'entry' may be used
   uninitialized in this function
 net/netlabel/netlabel_unlabeled.c:629: warning: 'entry' may be used
   uninitialized in this function

Signed-off-by: Paul Moore <paul.moore@hp.com>
Signed-off-by: David S. Miller <davem@davemloft.net>