Initialize optimizer for Coder

Hi, I want to use (the auto generated) code of the Registration Estimator app within Matlab and want to use it in C++.

My approach is to use Coder for this. But I have an issue during the "Check for issues" step within the wizard. I getting the (and a couple of others):

Attempt to extract field 'GradientMagnitudeTolerance' from 'mxArray'.

Error on the second line of this:

[optimizer, metric] = imregconfig('monomodal');
optimizer.GradientMagnitudeTolerance = 1.00000e-04;

What I understand so far is, that I have to use:

coder.extrinsic('imregconfig'); 
coder.extrinsic('optimizer');

In order to have it working. But the error still exists.

Any suggestions, how to avoid this error? / How to get rid of it?