Fixed the NullLogger to implement the HttpKernel interface again
merged branch stof/fix_null_logger (PR #6920)

This PR was merged into the master branch.

Commits
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b1d1168 Fixed the NullLogger to implement the HttpKernel interface again

Discussion
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Fixed the NullLogger to implement the HttpKernel interface again

| Q             | A
| ------------- | ---
| Bug fix?      | yes
| New feature?  | no
| BC breaks?    | no (reverting one introduced by mistake)
| Deprecations? | no
| Tests pass?   | yes
| Fixed tickets |
| License       | MIT
| Doc PR        | n/a

This BC breaking mistake has been reported in https://github.com/schmittjoh/JMSSecurityExtraBundle/pull/105#issuecomment-12908659