ipaccess-config: exit if no network interface is specified

ipaccess-config has to exit if no network interface is specified,
otherwise it uses argv[1] which has a uninitialized value.

openbsc/src/ipaccess/ipaccess-find.c

@@ -196,6 +196,7 @@ int main(int argc, char **argv)
 	if (argc < 2) {
 		fprintf(stdout, "you might need to specify the outgoing\n"
 			" network interface, e.g. ``%s eth0''\n", argv[0]);
+		exit(EXIT_FAILURE);
 	}
 
 	ifname = argv[1];