don't raise warnings when exception is thrown

`array_map()` raises a warning when an exception is thrown inside the
callback (see https://bugs.php.net/bug.php?id=55416). To avoid these
warnings, `selectorToXPath()` is applied inside the loop.
bug #12187 [CssSelector] don't raise warnings when exception is thrown (xabbuh)

This PR was merged into the 2.3 branch.

Discussion
----------

[CssSelector] don't raise warnings when exception is thrown

| Q             | A
| ------------- | ---
| Bug fix?      | yes
| New feature?  | no
| BC breaks?    | no
| Deprecations? | no
| Tests pass?   | yes
| Fixed tickets | #11947
| License       | MIT
| Doc PR        |

`array_map()` raises a warning when an exception is thrown inside the
callback (see https://bugs.php.net/bug.php?id=55416). To avoid these
warnings, `selectorToXPath()` is applied inside the loop.

Commits
-------

38e9623 don't raise warnings when exception is thrown
[Routing] fix inconsistencies in RequestContext
[Routing] add tests for RequestContext
minor #12190 [Routing] fix type inconsistencies in RequestContext (Tobion)

This PR was merged into the 2.3 branch.

Discussion
----------

[Routing] fix type inconsistencies in RequestContext

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

Fixed inconsistencies in RequestContext:

- [x] port setters and getters inconsistent with constructor (string vs int)
- [x] host should be lowercased for easier case-insensitivity, see #9072
- [x] fix setQueryString with null
- [x] fix return phpdoc typehint

Commits
-------

676c4a0 [Routing] add tests for RequestContext
f61607f [Routing] fix inconsistencies in RequestContext
Merge branch '2.3' into 2.5

* 2.3:
  [Routing] add tests for RequestContext
  [Routing] fix inconsistencies in RequestContext
  don't raise warnings when exception is thrown