During preview, template usage of $location->getContent() (in Twig that is location.content) will not work with a type exception. This can also be triggered by many other features in the system which by now use this API in some cases.

This is caused by missing content passed to the "fake" location object created by preview controller:

https://github.com/ezsystems/ezpublish-kernel/blob/7.5/eZ/Publish/Core/Helper/PreviewLocationProvider.php#L73-L81