misc: fix multiple NULL pointer sparse warnings

Those are fixes for the following warnings:

 pcap_mm.c:119:29: warning: Using plain integer as NULL pointer
 pcap_mm.c:141:29: warning: Using plain integer as NULL pointer
 ring.c:24:31: warning: Using plain integer as NULL pointer
 flowtop.c:1114:22: warning: Using plain integer as NULL pointer
 ifpps.c:1133:29: warning: Using plain integer as NULL pointer

Signed-off-by: Daniel Borkmann <dborkman@redhat.com>

1 files changed, 1 insertions, 1 deletions

diff --git a/flowtop.c b/flowtop.c
index b9d32cc..3e55079 100644
--- a/flowtop.c
+++ b/flowtop.c
@@ -1111,7 +1111,7 @@ static void *collector(void *null)
 	flow_list_destroy(&flow_list);
 	nfct_close(handle);
 
-	pthread_exit(0);
+	pthread_exit(NULL);
 }
 
 int main(int argc, char **argv)