list-validation columns contain confusing instructions when valid values don't exist

[allaway]

Describe the bug
Adding list as a validation rule triggers this instruction: From 'Selection options' menu above, go to 'Select multiple values', check all items that apply, and click 'Save selected values'

For columns with Valid Values, this makes sense. However, for columns without defined valid values, this is confusing, because the "Select multiple values" prompt will not include any options.

To Reproduce
Steps to reproduce the behavior:

1. Create an attribute with no valid values but with list validation, e.g. synonyms in this schema: https://docs.google.com/spreadsheets/d/15fwIhZw7YfhPkzOfQhj6zU_5-_7ywS05-L8qOjMIVdM/edit#gid=149825058
2. Generate json-ld
3. Generate manifest that includes attribute without valid values but with list, eg. https://docs.google.com/spreadsheets/d/1opQbHQzl5VWRb5H_FdCaQ1Qr0lrXc3pfut1mu3ULwqw/edit#gid=0
4. See prepopulated instructions for list validation column.

Expected behavior
I think in this case (list validation but no Valid Values listed), the instructions should instead provide information on how to format a list-column correctly for schematic to correctly interpret the multi-value list.