fixup! Do not lazy load forward relations

Author: Tim Csitkovics

rest_framework_json_api/serializers.py

@@ -185,7 +185,8 @@ def to_representation(self, instance):
                 context = getattr(self, '_context', {})
                 request = getattr(context.get('request', None), '_request', None)
                 get_dict = getattr(request, 'GET', None) if request is not None else {}
-                is_included = 'include' in get_dict and field.source in get_dict['include'].split(',')
+                includes = get_dict['include'].split(',') if 'include' in get_dict else []
+                is_included = field.source in includes
                 if not is_included \
                         and isinstance(field, ModelSerializer) \
                         and hasattr(instance, field.source + "_id"):