warnings: do not use zero as NULL

Found with smatch scan.

diff --git a/mtr.c b/mtr.c
index 17ae2651698ea8b20886c508821e0f074d80d484..dc99681ba6e7e0b8908b7b578266b6b247f947fe 100644 (file)
--- a/mtr.c
+++ b/mtr.c
@@ -390,7 +390,7 @@ static void parse_arg (struct mtr_ctl *ctl, int argc, char **argv)
 #ifdef SO_MARK
     { "mark",           1, NULL, 'M' }, /* use SO_MARK */
 #endif
-    { 0, 0, 0, 0 }
+    { NULL, 0, NULL, 0 }
   };
   static const size_t num_options = sizeof(long_options) / sizeof(struct option);
   char short_options[num_options * 2];