error on determine silhouette for k-means clustering

Hello

I'm using rapidminer version 8.1

I want to calculate the silhouette value for k-means clustering

For this purpose
I downloaded the plugin from the following URL:
http://korek.name/web/moje-tvorba/rapidminer-clustering_performance_plugin-average_silhouette-cophenetic_coefficient

My process image is as follows:

In this process, the following error occurs:

Does anyone know where the problem is?

thanks
regards