Geographical behaviour generates wrong INSERT statement in PostgreSQL if latitude/logitude not specified

Added "Geographical" behaviour to an entity:

 
ZipCode:
  actAs: [Geographical]
  columns:
    code: string
    [...]

Using the standard Symfony-generated admin manager, when trying to insert a new record without specifying both latitude and longitude, Doctrine generates a wrong INSERT statement for PostgreSQL, including latitude and longitude as '' (empty string)

 
Doctrine_Connection->exec('INSERT INTO zip_code (hidden, code,  country_id, latitude, longitude) VALUES (?, ?, ?, ?, ?)', array('false', '20133', '1', '', ''))

This cause this error:
SQLSTATE[22P02]: Invalid text representation: 7 ERROR: invalid input syntax for type double precision: ""

Workaround

explicitly specifying float type for latitude and longitude...

 
  actAs: 
    Geographical:
      latitude: {type: float}
      longitude: {type: float}

...still generate the column correctly as double precision in the database, but will not cause any error on inserting records.