If you upgrade phplist or import an old database, it will most probably show an error message similar or exact to the one in the picture below.

Error as it looks on the dashboard

The issue is that there is no more integer in that query, the field returns a boolean. So, the easiest way to solve this is to edit the ../admin/connect.php file and look for:

if (!empty($configInfo['hidden'])) {
$editable = false;
}

and replace it with:

if (!empty($configInfo['hidden'])) {
$editable = 0; //David updated it. it shoule be a integer value.
}

Fixed.