Use both valueType text and url in labeling interface

I'm trying to support both valueTypes for my labeling interface since I'm receiving tasks that can either be an s3 path to a text file, or just text. so my tasks will look like this:

```json
{
"data": {
"text_url": "s3://textfiles/file.txt"
}
}
```

Or this:

```json
{
"data": {
"text": "This is some inline text, do not worry"
}
}

```

Here is my labeling interface:

```xml

```

This works correctly for the `text_url` task files. But displays URL() not valid for `text` task files. Which means it doesn't find `text_url` field in my task.json and either passes an empty string or "None" or something like that and interprets it as a wrong URL.

Is it possible to either check for which field is present and go with that? Or just ignore text_url if it's not valid? Even though the second option will prevent me from seeing any relevant errors linked to a genuinely invalid URL.