Regex throws "Error: Cannot add shape [1] row to array with shape [2] rows"

[tankorsmash]

pad link for repro on pad's Uiua 0.12.0-dev.1

"foo(:?.)?" "foo"
regex

Error: Cannot add shape [1] row to array with shape [2] rows
  at 2:1
2 | regex
    ─────

Here's a rust playground with the regex set up if it helps.

[kaikalii]

Optional captures require fill. Like this

[tankorsmash]

Oh, fill is even mentioned in the docs, thanks!

If this is the only time regex can throw an error, having regex suggest fill in cases like this would be nice.