UTILS: Check that an iscsi url was provided on the command line before strdup()ing it

src/iscsi-readcapacity16.c

@@ -125,7 +125,9 @@ int main(int argc, char *argv[])
 		iscsi_set_log_level(iscsi, debug);
 	}
 
-	url = strdup(argv[optind]);
+	if (argv[optind] != NULL) {
+		url = strdup(argv[optind]);
+	}
 	if (url == NULL) {
 		fprintf(stderr, "You must specify the URL\n");
 		print_usage();