Must call super constructor in derived class before accessing 'this' or returning from derived constructor

```js
class Base {}

class Test extends Base {
constructor() {
super();
() => {
this.aa = 1;
}
}
}
```

```shell
$ npx buble test.js -n classes
```
```js
class Base {}

class A extends Base {
constructor() {
var this$1 = this;

super();
!function() {
this$1.aa = 1;
}
}
}
```