0 -> NULL (correct null pointer)

FossilOrigin-Name: e0b0bce3bad5d0576a91cb6eac0c961c7b2857f230dde5033dd4d441ab9729d3

src/ac/ac_main.c

@@ -63,7 +63,7 @@ static int parse_args(int argc, char *argv[])
 	int getopt_ret, option_index;
 
 	static struct option long_options[] = {
-		{"version", optional_argument, 0, 'v'},
+		{"version", optional_argument, NULL, 'v'},
 		{0, 0, 0, 0}
 	};
 	int o;