message: More handle_data fixing.
  I'm not sure why our existing tests didn't catch this...
diff: @@ -720,6 +720,8 @@ class _FuncGraph(ops.Graph):
  if ops._USE_C_SHAPES:
  if isinstance(tensor, ops.EagerTensor):
  handle_data = tensor._handle_data
  + if handle_data:
  + handle_data = handle_data.SerializeToString()
  else:
  handle_data = c_api.GetResourceHandleShapeAndType(
  tensor.graph._c_graph, tensor._as_tf_output())
  