Fixed NativeSessionStorage:regenerate when does not exists
merged branch lyrixx/fix-8460 (PR #8479)

This PR was submitted for the master branch but it was merged into the 2.2 branch instead (closes #8479).

Discussion
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 	[HttpFoundation] Fixed NativeSessionStorage:regenerate when does not exists

| Q             | A
| ------------- | ---
| Bug fix?      | yes
| New feature?  | no
| BC breaks?    | no
| Deprecations? | no
| Tests pass?   | yes
| Fixed tickets | #8460
| License       | MIT
| Doc PR        | -

**warning** I did not try to reproduce this bug, so I am not sure it fixes the issue. I just open a PR with the suggested patch. Tests for http foundation are OK. I am not sur it's the best way to fix this issue as I do not understand why symfony reach this code if $_SESSION is not set.

Commits
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f5d59fb [HttpFoundation] Fixed NativeSessionStorage:regenerate when  does not exists