Prevent segfault when trying to print an error message.
Prevent segfault when trying to print an error message.

Use <stdarg.h> to pass arguments correctly, as ack/util/util.c
already uses <stdarg.h> the same way.

Godzil/ack,Godzil/ack,Godzil/ack,Godzil/ack,Godzil/ack