Do not disconnect from the IRC server if the dummy channel is joined

src/irc/irc_client.cpp

@@ -645,6 +645,9 @@ void IrcClient::on_user_mode(const IrcMessage& message)
 
 size_t IrcClient::number_of_joined_channels() const
 {
+  if (this->dummy_channel.joined)
+    return this->channels.size() + 1;
+  else
     return this->channels.size();
 }