Badly implemented Boom like class can cause runtime error

### Runtime

na

### Runtime version

na

### Module version

all

### Last module version without issue

?

### Used with

standalone

### Any other relevant information

_No response_

### What are you trying to achieve or the steps to reproduce?

```js
const BadBoom = class extends Error { isBoom = true; };
Boom.isBoom(new BadBoom()); // true
Boom.isBoom(new BadBoom(), 404); // Cannot read properties of undefined (reading 'statusCode')
```

### What was the result you got?

An error because `err.output` is undefined in the `BadBoom` instance

### What result did you expect?

I know that `isBoom` is meant to work with object created only with any version of the `@hapi/boom` package but it could at least ensure that `err.output` is an object and that `err.output.statusCode` is a number.

What do you think ?