staging: lustre: fix api-ni.c issues found by Klocwork Insight tool

Pointer 'ni' checked for NULL at line 1569 may be passed to
function and may be dereferenced there by passing argument 1 to
function 'lnet_ni_notify_locked' at line 1621.
Signed-off-by: Dmitry Eremin <dmitry.eremin@intel.com>
Intel-bug-id: https://jira.hpdd.intel.com/browse/LU-4629
Reviewed-on: http://review.whamcloud.com/9386Reviewed-by: John L. Hammond <john.hammond@intel.com>
Reviewed-by: Isaac Huang <he.huang@intel.com>
Reviewed-by: Oleg Drokin <oleg.drokin@intel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/staging/lustre/lnet/lnet/router.c

@@ -1800,7 +1800,8 @@ lnet_notify(lnet_ni_t *ni, lnet_nid_t nid, int alive, unsigned long when)
 
 	lnet_notify_locked(lp, !ni, alive, when);
 
-	lnet_ni_notify_locked(ni, lp);
+	if (ni)
+		lnet_ni_notify_locked(ni, lp);
 
 	lnet_peer_decref_locked(lp);