[Escalated to WPML Developers team] Fatal error when activating Gravity Forms User Registration link in email

Gravity Forms User Registration Add-On clients receive an email with a link to activation.

The link looks like this:

<em><u>hidden link</u></em>

If you activate attempt to activate a user with Gravity Forms User Registration add-on and you have the default activation e-mail template overriden, when WPML is active, you will get a fatal error like this:

Fatal error: __clone method called on non-object in /wp-content/plugins/sitepress-multilingual-cms/sitepress.class.php on line 2875

This is happening because of hooking with gform_user_registered action with a priority of 10, and because of WPML expects that the query is set as an object.
However because of the modifications to the query by that hook, the expected query is NULL and this time, and that is why the error appears.

To resolve the problem:

There are two options:
#1 - Until this is fixed, do not use activation template override.
or
#2 - Patch /wp-content/plugins/sitepress-multilingual-cms/sitepress.class.php as mentioned in the errata page here: https://wpml.org/errata/issues-overriding-default-user-activation-template-gravity-forms-user-registration-add/
You need to go to:
/wp-content/plugins/sitepress-multilingual-cms/sitepress.class.php on line 2875
and change:

$wp_query = clone $this->wp_query;

with this code:

if(!is_object($this->wp_query)) {
    $this->wp_query = is_object( $wp_query ) ? clone $wp_query : null;
}

Please do mind that this fix is not very efficient, and may cause other issues that we might not have foreseen.