Surveys: No way to create a new person record while linking a survey submission

[richardolsson]

Description

When someone submits a survey, we call that a "survey submission". Survey submissions are usually submitted by unauthenticated users, and for that reason Zetkin does not automatically link a survey submission to a person. An organizer must manually find the record that represents the person that submitted the survey, and link it to the submission.

When trying to link a survey submission, if there is no person record that matches, there is currently no way of creating a new record to be linked to the submission.

Steps to reproduce

1. Go to https://app.dev.zetkin.org/organize/1/projects
2. Find any survey that has received submissions
3. Go to the submissions tab
4. In the list, make sure there are unlinked submissions
5. Double-click the cell where the missing link is
6. Type "acbd1234" into the search field that opens

Expected Behaviour

No person should be found. In the popper there should be a button that allows the user to create a new person object to be linked to the submission.

Actual Behaviour

No person is found, but the popper is then just empty. There is no button to create a new person record.

Screenshots (if you have any)