[Tests] Validation needed for Story importer to handle adding Places that don't exist in Terrastories

[rudokemper]

Describe the bug
Currently, when the Story CSV importer encounters a row with a Place (via the Place_name or Where_interviewed fields), if this Place does not exist yet in Terrastories, it will add the Place. That is all fine and dandy, but it's adding them with a (0,0) or null geography as per this related issue with the Place importer #598

To Reproduce
Steps to reproduce the behavior:

1. Download the Terrastories sample import spreadsheets and save the Stories as a CSV https://docs.google.com/spreadsheets/d/1Ir6TC5THEoQKk-98JZ5KpTjXd-R6yMmA/
2. Change one of the places in either Place_name or Where_interviewed fields to something else.
3. As a logged in admin or editor user for a community, navigate to the Stories page in the back end (/admin/stories?locale=en)
4. Import the CSV you just edited
5. The place will be created with null values, and showing up at 0,0 (off the coast of Africa) on the Terrastories map.

Expected behavior
Let's make it so that the Story importer does not add a Place that doesn't yet exist with null values to lat/longs, resulting in wonky null island placement.

Screenshots