Bug with trying to access an object field starting with underscore

https://rescript-lang.org/try?version=v10.1.2&code=DYUwLgBAZg9jEF4IENED4IG8BQEUG0AiAfQAZCBdbAX2yA

This
```rescript
let foo = a => {
  a["_0"]
}
```
is compiled to
```js
function foo(a) {
  return a[0];
}
```
instead of 
```js
function foo(a) {
  return a["_0"];
}
```

Reproduced in v11