Remove kubernetes cluster not longer available in GKE

I’ve activate the kubernetes integration for one of my repositories using Gitlab CI with Google Cloud Kubernetes Engine (GKE). After some first steps, I decide to remove the cluster via the Google Cloud Console.
After that removal, I cant’ remove that cluster in the list of my clusters under my gitab project / Operations / Kubernetes. There is always the following error:

An unknown error occurred while attempting to connect to Kubernetes.

Troubleshooting tips:

    Check your cluster status
    Make sure your API endpoint is correct
    Node calculations use the Kubernetes Metrics API. Make sure your cluster has metrics installed 

I know, it should be better to remove it on gitlab side first and afterwards on GKE …
How can a cluster be removed which is not longer existing on GKE side ?

kind regards

Are you following the Removing integration steps described at Adding and removing Kubernetes clusters | GitLab, which allows you to drop the GitLab relations holding onto the cluster?

thanks for the hint, I’ve already tried Remove integration and resources but this didn’t work. But Remove integration did the job.

kind regards

Dominik Hirt