In MultiSelect when the value is set initially and the mapValueTo option is set to 'dataItem', if the user first open and close the popup, the last item can not be removed and an error 'c.select(...).done is not a function' is thrown.
As the Dojo above does not use a remote valueMapper below is a sample project where a remote valueMapper method is implemented
WebApplication3.zip
The last item can not be removed and an error 'c.select(...).done is not a function' is thrown in the browser`s console.
The other items except the last one can be removed as expected. Also, all items can be removed initially in case the popup has not been opened and scrolled to the last item from the value.
It should be possible to remove all items displayed in the MultiSelect input, even in a scenario where the popup has been opened and closed.