[Debug] preserve modified error level
[Debug] throw even in stacking mode to preserve code paths
minor #10988 [Debug] preserve modified error level (nicolas-grekas)

This PR was merged into the 2.5 branch.

Discussion
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[Debug] preserve modified error level

| Q             | A
| ------------- | ---
| Bug fix?      | yes
| New feature?  | no
| BC breaks?    | no
| Deprecations? | no
| Tests pass?   | yes
| Fixed tickets | none
| License       | MIT
| Doc PR        | none

Minor edge case, but still a bug fix.
Replaces https://github.com/symfony/symfony/pull/10978

Commits
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e40b717 [Debug] preserve modified error level
Merge branch '2.5'

* 2.5:
  [TwigBridge][Trans]set %count% only on transChoice
  [Debug] throw even in stacking mode to preserve code paths
  [Debug] preserve modified error level
  [DomCrawler] Fixed a forgotten case of complex XPath queries
  bumped Symfony version to 2.4.6
  updated VERSION for 2.4.5
  updated CHANGELOG for 2.4.5
  bumped Symfony version to 2.3.16
  updated VERSION for 2.3.15
  updated CHANGELOG for 2.3.15