This is related to CVE-2009-3555, an MITM vulnerability in the SSL/TLS protocols, reported in 2009. While older OpenSSL versions had the SSL_OP_LEGACY_SERVER_CONNECT option enabled by default when using SSL_OP_ALL with SSL_CTX_set_options(), to allow connections to unpatched servers, newer versions of OpenSSL do not.
The issue is not whether the site you are using is safe/unsafe. It is that, because the SSL on your IRC server has not been updated, possibly since 2009, your SSL connections to it are not secure.
Have you contacted the owner of the server to ask them to update their server?