'zlib output compression' handler

If you change zlib output compression setting in
between ob_start, ob_end_clean or ob_end_flush, 
you will get: ob_end_flush() failed to delete buffer zlib output compression.

Added - 1853: 

 else if ( $handler === 'zlib output compression' ) {
    if (ob_get_level()) {
        while (@ob_end_clean());
    }
 }