Calling environment.set(data) when subclassing doesn't set data

Example:
```js
const env = new Environment({
  test: "123"
});
env.get("test"); // returns null
```

It does work if you call `set` separately:
```js
const env = new Environment();
env.set({
  test: "123"
});
env.get("test"); // returns "123"
```