mpd: fix FD leak by resetting connection on MPD_ERROR_SYSTEM errors

Co-authored-by: Alexays <13947260+Alexays@users.noreply.github.com>

src/modules/mpd/mpd.cpp

@@ -323,6 +323,7 @@ void waybar::modules::MPD::checkErrors(mpd_connection* conn) {
     case MPD_ERROR_SYSTEM:
       if (auto ec = mpd_connection_get_system_error(conn); ec != 0) {
         mpd_connection_clear_error(conn);
+        connection_.reset();
         throw std::system_error(ec, std::system_category());
       }
       G_GNUC_FALLTHROUGH;