[12.x] Fix TypeError in Http::retry() when callback type-hints Throwable

[hamedelasma]

Summary

Fixes #59012

Http::retry() throws a TypeError when the when callback type-hints Exception or Throwable and the response is not a 4xx/5xx (e.g., a 3xx redirect). This happens because $response->toException() returns null for non-failed responses, and passing null to a callback expecting Exception causes the TypeError.

Fix: Extract $response->toException() into a variable first. If it's null, skip calling the when callback and default $shouldRetry to true. Applied in both send() and handlePromiseResponse().

Changes

File	Change
PendingRequest.php	Guard against null exception before invoking when callback in both sync and async paths
HttpClientTest.php	Add 2 tests for Exception and Throwable type-hints with non-4xx/5xx responses

Test Plan

• testRetryWhenCallbackWithExceptionTypeHintDoesNotThrowTypeErrorForNon4xxOr5xxResponses
• testRetryWhenCallbackWithThrowableTypeHintDoesNotThrowTypeErrorForNon4xxOr5xxResponses
• All existing retry tests pass