message: Better handling when `operators` is `None` instead of `[]`.
diff: @@ -293,7 +293,7 @@ def GenerateGraph(subgraph_idx, g, opcode_mapper):
  second = {}
  pixel_mult = 200 # TODO(aselle): multiplier for initial placement
  width_mult = 170 # TODO(aselle): multiplier for initial placement
  - for op_index, op in enumerate(g["operators"]):
  + for op_index, op in enumerate(g["operators"] or []):
  for tensor_input_position, tensor_index in enumerate(op["inputs"]):
  if tensor_index not in first:
  @@ -487,6 +487,7 @@ def CreateHtmlFile(tflite_input, html_output):
  html += GenerateTableHtml(g["tensors"], tensor_keys_to_display)
  # Print the ops.
  + if g["operators"]:
  html += "<h3>Ops</h3>\n"
  html += GenerateTableHtml(g["operators"], op_keys_to_display)
  