Symfony version(s) affected: 4.2.4

Description
Running the command "debug:container kernel --format=json" results in an error
`In Descriptor.php line 292:

[Symfony\Component\Debug\Exception\FatalThrowableError]
Argument 1 passed to Symfony\Bundle\FrameworkBundle\Console\Descriptor\Descriptor::getClassDescription() must be of the type string, null given, called in ####\vendor\symfony\framework-bundle\Console\Descriptor\JsonDescriptor.php on line 223
`

How to reproduce

• Download fresh copy of the symfony/skeleton
• Run "bin\console debug:container kernel --format=json"

Possible Solution
Notable that ServiceID kernel has no classname associated with it

Believe this is related to this: #28117