Big Menu throw critical error when domain language negotiation in enabled

Hello Steve,
Your patch redirects the user to the root links no matter what menu_link is being edited.
The issue comes from the $this->getRedirectDestination()->get() response, it changes depending on the language negotiation settings.
If no language or language negotiation based on url prefix it returns a relative URL starting with "/".
If language negotiation based on domain it returns an absolute URL starting with "http$://" and Url::fromUserInput fails.

We'll need some tests here