It doesn't look like you saved after deleting the value from the 'Test' field. You deleted the value, set a different value, then saved. Can you try deleting the value, then saving?
EditForm1.DataSource: Testing
EditForm1.Item: BrowseGallery1.Selected
Fields:

I'm also not seeing the value updated in SharePoint.

Also, in case you're wondering, the code for the save button on the edit screen is SubmitForm(EditForm1).