• Fix build with IPV6 disabled

Obtained from: https://github.com/traviscross/mtr/commit/3d1352ca93efca2f8c4be7ccd16cbe2472b4fff0
PR: 214731 [1]
Submitted by: <sergey@akhmatov.ru> [1], Iain Grant <iain.grant@stream-technologies.com> (via email)