In my Google spreadsheet, I have a column G of dates that interviews are/have been scheduled on. There is a validation set on it to validate for dates with a warning. Every once in a while, when someone was adding historical data but didn't know the right date they just put an x that the event has occurred (or cancelled if it was cancelled, or a variety of other non-blank statuses).

I'm now trying to use Query to get for all rows where that column is empty (regardless of validation)

I have

=QUERY('Interview Planning'!A:G, "select D, A, F, G WHERE G IS NULL")

But seem to be getting back any row for which G is not a valid date, not just where it is NULL.

How do I make it ignore the validation?

Demo of the issue:
https://docs.google.com/spreadsheets/d/14HmBvzjjo_z88WtfKAwYckIUNruTA8ivZEUaefKj2qw/edit?usp=sharing