Fixed #65 -- Disallow None value for product default prices

src/pretix/base/migrations/0007_auto_20150726_1430.py

@@ -0,0 +1,20 @@
+# -*- coding: utf-8 -*-
+from __future__ import unicode_literals
+
+from django.db import models, migrations
+
+
+class Migration(migrations.Migration):
+
+    dependencies = [
+        ('pretixbase', '0006_auto_20150726_1420'),
+    ]
+
+    operations = [
+        migrations.AlterField(
+            model_name='item',
+            name='default_price',
+            field=models.DecimalField(verbose_name='Default price', default=0, decimal_places=2, max_digits=7),
+            preserve_default=False,
+        ),
+    ]