[Twig] fixed TwigEngine::exists() method when a template contains a syntax error (closes #88546)
merged branch fabpot/twig-engine-exists (PR #8547)

This PR was merged into the 2.2 branch.

Discussion
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[Twig] fixed TwigEngine::exists() method when a template contains a syntax error (closes #8546)

| Q             | A
| ------------- | ---
| Bug fix?      | yes
| New feature?  | no
| BC breaks?    | no
| Deprecations? | no
| Tests pass?   | yes
| Fixed tickets | #8546
| License       | MIT
| Doc PR        | n/a

Commits
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ae7fa11 [Twig] fixed TwigEngine::exists() method when a template contains a syntax error (closes #88546)