Issue with selector with regex in return

Nobody has claimed this yet.

I have seen a few examples like below:

```
selector: function(match) {
regex = new RegExp(match, 'i')
return {'profile.firstName': regex}
}
```

I am actually trying the code above. If I put a string in place of `regex`, it is passed and works correctly, but when I use the `regex` variable, the output sent to query looks like this `'profile.firstName': {} } { limit: 10, sort: { _id: 1 } }`. Notice the `regex` portion is missing.

Anyway, I am not sure why this doesn't work yet. Any thoughts?

No file or test is named; begin at the selector callback and the query-serialization entry point described in the report. Reproduce the difference between returning a string and a RegExp, then determine whether regex selectors are supported and verify that the resulting query is preserved or the limitation is documented.

Written by the indexing model from the issue text.