PointField does not allow setting blank=True and null=False

[George Tantiras]

The following code worked nicely in Python 3.3 / Django 1.6.x:

from django.contrib.gis.db import models

class Coordinates(models.Model):

    point = models.PointField(blank=True,null=False)
    objects = models.GeoManager()

However, in Python 3.3 / Django 1.7.1:

$ ./manage.py makemigrations
$ ./manage.py migrate

...
ValueError: String or unicode input unrecognized as WKT EWKT, and HEXEWKB.

[Tim Graham]

​PR

[Tim Graham <timograham@…>]

In d6d55368d45ca05c4c08c4981f9dba5c9b2bd72e:

Fixed #23731 -- Fixed migrations crash when adding blank GeometryFields on PostGIS.

Thanks raratiru for the report and Claude Paroz for review.

[Tim Graham <timograham@…>]

In 17205a98ed0e4fb2a4ce9137508ee65efc448c07:

[1.7.x] Fixed #23731 -- Fixed migrations crash when adding blank GeometryFields on PostGIS.

Thanks raratiru for the report and Claude Paroz for review.

Backport of d6d55368d4 from master