Fix AttributeError bug (#170)

* support handling streaming in SGP * fix bug

Author: khshah6

launch/model_endpoint.py

@@ -305,7 +305,7 @@ def __next__(self):
  """Uses server-sent events to iterate through the stream."""
  event = self.events.__next__()
  data = json.loads(event.data)
- result = data.get("result", {})
+ result = data.get("result", {}) or {}
  return EndpointResponse(
  client=None,
  status=data["status"],