[DI] Fixed bug requesting non existing service from dumped frozen container
merged branch WouterJ/di_alias_dumper_bug (PR #8435)

This PR was squashed before being merged into the 2.3 branch (closes #8435).

Discussion
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[DI] Fixed bug requesting non existing service from dumped frozen container

When dumping a frozen container without aliases, the method `Container::has()` will throw a *"Warning: array_key_exists() expects parameter 2 to be array, null given"* warning. It's because `PhpDumper::addAliases` returns `''` if no aliases are given. This will work for a normal constructor, because it calls the `Container::__construct` method, but the frozen constructor doesn't do that. So it requires a `$this->aliases = array();` in the constructor.

This PR fixes this bug (and adds the test). Bug is introduced in #8252 and 63367a3d5615ff65251ccee4f73223107275f65f

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

Commits
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8bb4e4d [DI] Fixed bug requesting non existing service from dumped frozen container
CookieJar remove unneeded var, Client remove unneeded else
merged branch entering/browser-kit-beautify-code (PR #8432)

This PR was submitted for the master branch but it was merged into the 2.3 branch instead (closes #8432).

Discussion
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[BrowserKit] CookieJar remove unneeded var, Client remove unneeded else

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

Commits
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10c6799 [BrowserKit] CookieJar remove unneeded var, Client remove unneeded else