Some nodes returned a blank lat,lon and grid_square differently than
others that were also blank.

This was causing issues when writing to the SQL database.
get-map-info would throw this error when it would happen:
"Could not send to SQL. Incorrect double value: '' for column 'lat' at
row 1"

Fix:
Any blank lat || lon now get converted to a single "0".
Any blank grid_square now gets converted to a NULL.