message: make op_level_cost_estimator more robust with "random" input.
diff: @@ -773,6 +773,11 @@ int64 OpLevelCostEstimator::CountConv2DOperations(
  DCHECK(op_info.op() == kConv2d || op_info.op() == kDepthwiseConv2dNative)
  << "Invalid Operation: not Conv2D nor DepthwiseConv2dNative";
  + if (op_info.inputs_size() < 2) { // Unexpect inputs.
  + *found_unknown_shapes = true;
  + return 0;
  + }
  +
  ConvolutionDimensions conv_dims = ConvolutionDimensionsFromInputs(
  op_info.inputs(0).shape(), op_info.inputs(1).shape(), op_info,
  found_unknown_shapes);
  