Singleton pattern

Hi!

We are from Nextend Social Login and we had a received some requests to make our plugin compatible with Woocommerce User Email Verification.

By default Woocommerce User Email Verification prevented the login with Nextend Social Login as well.

We made a fix for this problem and we also needed to remove the action that sends the email verification when the user connects with a provider like Facebook, Google etc…

The problem is that, there is an issue with the singleton pattern of the class XLWUEV_Woocommerce_Confirmation_Email_Public in wp-content/plugins/woo-confirmation-email/public/class-xlwuev-woocommerce-confirmation-email-public.php.

The description of the issue:
We are removing the action like:

remove_action('user_register', array(
                XLWUEV_Woocommerce_Confirmation_Email_Public::instance(),
                'custom_form_user_register'
            ), 10);

However XLWUEV_Woocommerce_Confirmation_Email_Public::instance() creates a new instance every time when it is called, instead of referring to the original one.

According to the instance function:

public static function instance() {
		if ( null == self::$ins ) {
			return new self;
		}

		return self::$ins;
	}

it should refer to the original one, if one already exists.

The fix for this problem is that to add
self::$ins = $this;
at the constructor like:

public function __construct() {
	    self::$ins = $this;
...
}

We are looking forward to your feedback.

Best regards,
Laszlo.