This should actually be a feature request.  Many ISPs and/or personal routers do not offer v6 routing capabilities yet, but DNS will still return both the "A" and "AAAA" records for a hostname.  If the system has a link-local v6 address defined, it may attempt to connect to the v6 address when no route exists to it.

Suggest offering an "Auto", "IPv4", "IPv6" selection choice in the "Server" specification window, similar to how PuTTY does it.