Steps to reproduce the issue

login to frontend with super admin rights.
edit breadcrumbs module

Expected result

some kind of edit form

Actual result

0 Call to undefined method Joomla\Component\Modules\Administrator\Model\ModulesModel::getItem()

I have also seen on my other installation that the edit icon top right of a module, will launch a /administrator/ url to edit the module sometimes... that one works only if you are logged into the admin console as well as the frontend.

System information (as much as possible)

Unique ID 707d2b7806a60debd39e54bb17bfc8cf98c6de6f
PHP Version 7.1.11
DB Type mysqli
DB Version 5.7.20
CMS Version 4.0.0
Server OS Darwin 17.3.0