That is impossible ( in DEV mode ) to edit a Content Type for example.

It works in PROD (because the Notice is not triggered)
but
https://github.com/ezsystems/PlatformUIBundle/blob/master/Controller/ContentTypeController.php#L150
The array is still empty..

CRITICAL - Uncaught PHP Exception Symfony\Component\Debug\Exception\ContextErrorException: "Notice: Undefined offset: 0" at vendor/ezsystems/platform-ui-bundle/Controller/ContentTypeController.php line 150 

I figured that out! That's a mistake in the siteaccess configuration.

See the PR in comment