``get_model_data`` fails when trying to extract model data with monotonized features

[Krzys25]

Hello,

I encountered an issue when trying to use the get_model_data function to extract model data from an ExplainableBoostingClassifier instance with monotonized features.

Steps to Reproduce:

1. Fit an ExplainableBoostingClassifier instance.
2. Apply the monotonize method for one of the features.
3. Attempt to extract the model data using get_model_data.

Expected Behavior: The function should return the model data successfully.

Actual Behavior: The function fails with a TypeError in this line, and upon further investigation, I noticed that the entry in ebm.standard_deviations_ for the feature I applied monotonize to is being set to None.

Workaround: Currently, I'm manually replacing the None value with a placeholder value, but I believe this should be handled gracefully by the library itself.

Please let me know if any further information is required or if there's a known solution to this problem.

Thanks in advance for your help.

Best, Krzysztof