```
webpack:///../lib/@avocado/packages/entity/trait.js?:29
      entity.on("".concat(type, ".trait-").concat(traitType), listeners[type], this);
```

This is because you subclassed `Trait` but forgot to pass through the arguments
from your subclass constructor to the superclass constructor. Always default
to writing your Trait definition like:

```
class MyTrait extends Trait {

  initialize() {
    // ...
  }

}
```

All trait initialization should be done in `initialize`.

If you need really need to access arguments in your subclass constructor, opt
to pass along `arguments` instead, such as:

```
class MyTrait extends Trait {

  constructor(entity, params, state) {
    super(...arguments);
    // ...
  }

}
```