Bug: Heregex escaped space before comment includes comment in transpiled regex

### Input Code

```coffee
///
a\ # this is a bug
///
```

### Expected Behavior

```javascript
// this is a bug
/a /;
```

### Current Behavior

```javascript
// this is a bug
/a #thisisabug/;
```

* CoffeeScript version: 2.7.0
