Call to a member function isOpen() on null

After trying to change the icon in the admin panel, i get following error:

Call to a member function isOpen() on null

Error should be caused by following line, but i haven’t changed it and can’t find an issue

<li<?php e($contact->isOpen(), ' class="uk-active"') ?>>

I did change the default language prior to this error as well. But changing it back does not help finding the cause of this error.

Can someone help here?

The $contact variable is null. This probably means the contact page slug has been changed.

Can you show the line where $contact is defined?