Set `Event` to something other than `None` at runtime

### How do you use Sentry?

Sentry Saas (sentry.io)

### Version

1.44.0

### Steps to Reproduce

See https://github.com/getsentry/sentry-python/issues/2909#issuecomment-2028659630. Simply running the code (i.e. with `python` not `pytest`) also causes the problem.

### Expected Result

No error

### Actual Result

```
TypeError: unsupported operand type(s) for |: 'NoneType' and 'NoneType'
```