警告：mysql_query（）：25不是第60行/home/.../classes/class_core.php中有效的MySQL-Link资源[关闭]

I have gone through all the related answers.

when I'm using http://sitename this doesn't occur, but when I use https://sitename this error occurs

Warning: mysql_query(): 25 is not a valid MySQL-Link resource in /home/.../classes/class_core.php on line 60

here's the code

function &execute_query($buffered = true, &$link) {
    $this->connection_recent = &$link;

    $this->querycount++;
//line 60 is below
    if ($queryresult = $this->functions[($buffered ? "query" : "query_unbuffered")]($this->sql, $link)) {
        $this->sql = "";
        return $queryresult;
    }

    $this->sql = "";
}

I'm using hostgator business account.

I got through by changing

$this->connection_recent = &$link;

into

$this->connection_recent = $this->connection_master;

Hope this helps someone someday :)