Adjusted  model definition in GeoDjango tutorial.
The example uses the world border data set, where
one of the entries has a null field value.
@@ -203,7 +203,7 @@ model to represent this data::
name = models.CharField(max_length=50)
area = models.IntegerField()
pop2005 = models.IntegerField('Population 2005')
- fips = models.CharField('FIPS Code', max_length=2)
+ fips = models.CharField('FIPS Code', max_length=2, null=True)
iso2 = models.CharField('2 Digit ISO', max_length=2)
iso3 = models.CharField('3 Digit ISO', max_length=3)
un = models.IntegerField('United Nations Code')
