Merged in [13303] from rcross@amsl.com:

Fixes #2211.  Session admin edit fails if no resources selected.
 - Legacy-Id: 13319
Note: SVN reference [13303] has been migrated to Git commit 9ba73e70a2

ietf/meeting/migrations/0051_auto_20170511_0449.py

@@ -0,0 +1,20 @@
+# -*- coding: utf-8 -*-
+# Generated by Django 1.10.7 on 2017-05-11 04:49
+from __future__ import unicode_literals
+
+from django.db import migrations, models
+
+
+class Migration(migrations.Migration):
+
+    dependencies = [
+        ('meeting', '0050_add_room_resources'),
+    ]
+
+    operations = [
+        migrations.AlterField(
+            model_name='session',
+            name='resources',
+            field=models.ManyToManyField(blank=True, to='meeting.ResourceAssociation'),
+        ),
+    ]

ietf/meeting/models.py

@@ -917,7 +917,7 @@ class Session(models.Model):
     remote_instructions = models.CharField(blank=True,max_length=1024)
 
     materials = models.ManyToManyField(Document, through=SessionPresentation, blank=True)
-    resources = models.ManyToManyField(ResourceAssociation)
+    resources = models.ManyToManyField(ResourceAssociation, blank=True)
 
     unique_constraints_dict = None