Allow empty URL for an image

boards/migrations/0052_auto_20161120_1344.py

@@ -0,0 +1,20 b''
+# -*- coding: utf-8 -*-
+# Generated by Django 1.9.5 on 2016-11-20 11:44
+from __future__ import unicode_literals
+
+from django.db import migrations, models
+
+
+class Migration(migrations.Migration):
+
+    dependencies = [
+        ('boards', '0051_auto_20161013_1037'),
+    ]
+
+    operations = [
+        migrations.AlterField(
+            model_name='attachment',
+            name='url',
+            field=models.TextField(blank=True, null=True),
+        ),
+    ]

boards/models/attachment/__init__.py

@@ -46,7 +46,7 b' class Attachment(models.Model):'
     mimetype = models.CharField(max_length=50, null=True)
     hash = models.CharField(max_length=36, null=True)
     alias = models.TextField(unique=True, null=True, blank=True)
-    url = models.TextField(null=True)
+    url = models.TextField(null=True, blank=True)
 
     def get_view(self):
         file_viewer = None