Error: Admin > Accounts > Configuration

I am using Grav with Plugin Flex-Objects installed just for Admin.
When I try to go to Admin > Accounts > Configuration (TAB) I get an error.

in file:
system/src/Grav/Framework/Flex/FlexDirectory.php

in line 244:
return $grav['config']->get($path);

error:
Return value of Grav\Framework\Flex\FlexDirectory::loadDirectoryConfig() must be of the type array, null returned

I have tested it with user Admin rights and 2 seperate installations.
Grav, Admin and Flex-objects are up to date.

@epb, Appears to be a known issue. See issue Clicking Configuration button throws an error #2166 at repo of Admin.