Fix an edge case with ansi hyperlinks

```r
cli::cli_text("{.path {''}}")
```
broke because the path became `NULL` in
`parse_file_link_params()` and it was fed to
`path.expand()` which failed.

Author: gaborcsardi

R/ansi-hyperlink.R

@@ -89,6 +89,7 @@ parse_file_link_params <- function(txt) {
   matches <- re_match(txt, pattern)
   ret <- as.list(matches)
   ret[!nzchar(ret)] <- list(NULL)
+  if (is.null(ret[["path"]])) ret[["path"]] <- ""
   ret
 }