Fixed primary key null not being respected

[roland-d]

Problem

If no primary key value is passed to the publish method it is now not being respected as it is turned into an array, the loaded state is not being used as should. This PR fixes this issue introduced in #6893

Test instructions

1. Apply pull request Fix JTable publish method error #6900 first

2. Add the code below to the file administrator/component/com_cpanel/cpanel.php after line 10.
   This will show the problem as we first unpublish the record and then publish it.

    require_once JPATH_ADMINISTRATOR.'/components/com_contact/tables/contact.php';
    $row = JTable::getInstance('Contact', 'ContactTable');
    $row->load(1);
    $row->publish(1, 0);
    $row->publish();
    echo 'Published: ' . $row->published;

3. Load the administrator control panel and it shows Published: 0. This is wrong because we just published the record.

4. Apply the patch

5. Load the administrator control panel and it shows Published: 1. This is correct because we just published the record.

6. Testing finished

[joomdonation]

@test: Success.

[zero-24]

@test success RTC Thanks 😄

[Kubik-Rubik]

Thank you @roland-d for this fix. Merged this PR!