Visual editing of document with a multi select field results in unexpected behaviours

While opening the visual editor in the channel manager for a document that contains a multi-select, the UI shows a change has been made by showing an enabled "Discard" and "Save" button. Also when you try to close the editor you get the dialogue that changes have been made. This should not happen.

We can also reproduce this in the GoGreen demo website, please see the reproduction steps and attached image.

Steps to reproduce:

1. Go to: https://cms.demo.onehippo.com and login
2. Open the "events" page in the channel manager (I used the Dutch website)
3. Click the edit content button for the following content: "Feest voor de planeet"