In some situations, the c-ares lookup can return NULL instead of
a list of addresses. In this situation, we need to avoid
dereferencing NULL.
This patch adds a log message and sets the count to zero so it is
handled appropriately below.
This patch fixes the crash seen in
https://bugzilla.redhat.com/show_bug.cgi?id=880571
This may actually be due to a bug in c-ares, but we should be defensive
anyway.