eval_select() returns unnamed vector sometimes

Is this intended?

``` r
tidyselect::eval_select(rlang::quo(a), rlang::set_names(letters))
#> a 
#> 1
tidyselect::eval_select(rlang::quo("a"), rlang::set_names(letters))
#>   
#> 1
```

<sup>Created on 2020-02-13 by the [reprex package](https://reprex.tidyverse.org) (v0.3.0)</sup>