Allow null for FalafelDateTime form fields

tailbone/forms/types.py

@@ -87,7 +87,7 @@ class FalafelDateTime(colander.DateTime):
 
     def serialize(self, node, appstruct):
         if not appstruct:
-            return colander.null
+            return {}
 
         # cant use isinstance; dt subs date
         if type(appstruct) is datetime.date:
@@ -111,6 +111,9 @@ class FalafelDateTime(colander.DateTime):
         if not cstruct:
             return colander.null
 
+        if not cstruct['date'] and not cstruct['time']:
+            return colander.null
+
         try:
             date = datetime.datetime.strptime(cstruct['date'], '%Y-%m-%d').date()
         except: