Symfony version(s) affected: 5.2

Description
When the environment (either when passing it with --env in CLI, or the APP_ENV env variable), is an empty string, a hard to debug error comes up:

In BaseNode.php line 340:
                                                                                                                  
  Configuration path "security.access_control" cannot be overwritten. You have to define all options for this path, and any of its sub-paths in one configuration section.             

How to reproduce

On a fresh symfony project run:

bin/console --env=''

When a non existing environment is provided, everything works 'normally'. The error only occurs if the environment is empty. e.g.

bin/console --env='foo'

Possible Solution

Detect an empty environment as a bug, and report it to the user.