Crash when handling memory-related errors with `beforeSend` callback or screenshot capturing enabled

Memory-related fatal error handling may trigger secondary crashes when `beforeSend` or screenshot capture is enabled on sentry-native platforms (see https://github.com/getsentry/sentry-unreal/issues/991#issuecomment-3383340269).

### Related issues
- https://github.com/getsentry/sentry-unreal/issues/992
- https://github.com/getsentry/sentry-unreal/issues/991