When a new geo field is defined after nodes have been created, a faulty record is created in the database

To replicate this error, create a new node with some data.

Then create a new geo field for that node type. Don't edit your actual node.

Then do the following query (I did it in MySQL):

SELECT * FROM `content_field_YOURFIELDNAME`

You'll get one record returned even though you haven't inputted any data into the node:

vid: 1
nid: 1
delta: 0
field_line_wkt : NULL
field_line_lat : NULL
field_line_lon: NULL
field_line_geo : 

If you edit your node then save it, the query returns no rows, as is proper

This is problematic because contributed field formatters that use geo will get a $element that reports that it has a valid field record, but that actually just contains blank and null values.