Warning: array_flip(): Can only flip STRING and INTEGER values! in EntityStorageBase

This issue is a showstopper with the latest Drupal core.

I get WSOD when displaying a node comment form with Mollom enabled. This means the node itself fails to show if the comment form is on the same page.

The log shows:

Notice: Array to string conversion in Drupal\Core\Config\Entity\ConfigEntityStorage->doLoadMultiple() (line 181 of /home/ross/devel/d8test/www/core/lib/Drupal/Core/Config/Entity/ConfigEntityStorage.php).

I have solved it and I'm happy to submit a patch but I'm still quite new to most of Drupal 8 so ... perhaps there is more to it than I'm seeing.

In mollom.module, mollom_form_alter, line 303 we have this:

if (isset($forms['protected'][$form_id])) {
  $protected_form_id = [$form_id];
}

I don't think $protected_form_id should be turned into a one element array. The form displays correctly if I remove the square brackets so $protected_form_id is just a string.

Then there is another problem when I attempt to post a comment ("reason" can't be null) but I'll create another issue for that.