Incorrectly removing code

bool.js:

``` js
export default true
```

index.js:

``` js
import bool from "./bool"

const hs = document.documentElement.style

if (bool) {
    hs.color = "#222"
}

console.log("hey")
```

command:

```
rollup index.js
```

output:

``` js
console.log("hey")
```

😢 
