Fix push notification registration request

website/pushnotifications/api/serializers.py

@@ -10,6 +10,7 @@ class DeviceSerializer(ModelSerializer):
 
     receive_category = ManyRelatedField(
         allow_empty=True,
+        required=False,
         child_relation=PrimaryKeyRelatedField(allow_empty=True,
                                               queryset=Category.objects.all(),
                                               required=False)

website/pushnotifications/api/viewsets.py

@@ -29,7 +29,8 @@ class DeviceViewSet(ModelViewSet):
             )
         except Device.DoesNotExist:
             pass
-        if len(serializer.validated_data['receive_category']) > 0:
+        data = serializer.validated_data
+        if 'receive_category' in data and len(data['receive_category']) > 0:
             serializer.save(user=self.request.user, language=language)
         else:
             categories = [c.pk for c in Category.objects.all()]