With the default of `multi=TRUE`, `choose.files()` returns `character(0)` when the user presses Cancel. However, with `choose.files(multi=FALSE)` and the user presses Cancel, it returns a zero-length string, `""`.

As an example, both times I press "Cancel":

```r
choose.files()               # press Cancel
## character(0)
choose.files(multi = FALSE)  # press Cancel
## [1] ""
```

Based on the verbiage in the Rd: *"If the user cancels the dialog, then zero files are returned"*, I would expect the following behavior:

```r
choose.files()               # press Cancel
## character(0)
choose.files(multi = FALSE)  # press Cancel
## character(0)
```

This could be interpreted as a bug in the code or an inconsistency in the documentation; I see it more as the former.

I truly appreciate the efforts of the R dev team. Thank you for your continued efforts!

-bill