If you create a Scrum board Quick Filter with an empty query, then add a query that checks for a status that doesn't exist, you can no longer edit or delete the Quick Filter – it just gets stuck complaining about the status that doesn't exist.

Repro steps:
1) On a scrum board, create a filter with an empty JQL field.
2) Edit the JQL for the query to be: "status!=badstatus" and save this change. It will actually let you save it.
3) Try to delete the filter. Nothing happens in the UI, the filter just stays there.
4) Edit the JQL for the query to be: "assignee is EMPTY" and click the "UPDATE" button. The edit fails to save, and you get this validation error on the page complaining about the OLD JQL, not the new: "The value 'badstatus' does not exist for the field 'status'."

When I run the DELETE HTTP request manually to try to delete the filter, this is what I get:

{
  "errorMessages": [],
  "errors": {
    "query": "The value 'badstatus' does not exist for the field 'status'."
  }
}