bug #19564 Added class existence check if is_subclass_of() fails in compiler passes (SCIF)
bug #19564 Added class existence check if is_subclass_of() fails in compiler passes (SCIF)

This PR was merged into the 2.7 branch.

Discussion
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Added class existence check if is_subclass_of() fails in compiler passes

| Q             | A
| ------------- | ---
| Branch?       | 2.7
| Bug fix?      | no
| New feature?  | yes
| BC breaks?    | no
| Deprecations? | no
| Tests pass?   | yes
| Fixed tickets | comma-separated list of tickets fixed by the PR, if any
| License       | MIT
| Doc PR        | no

Backport of #19342 to 2.7 branch

Commits
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77adea7 Added class existence check if is_subclass_of() fails in compiler passes

symfony/EventDispatcher,symfony/event-dispatcher