🐛 Autocomplete: undefined param in optionDiabled

[oddvernes]

resolves #3677

For some reason selectedItems (returned from useMultipleSelection from downshift) contains an array with null ([null]) if you have a controlled singleselect and update selectedOptions with an empty array from the outside. This then causes the component to crash if optionDisabled is defined and tries to read a property from null. I have fixed this by adding an extra null check when creating the selectedDisabledItemsSet

[torleifhalseth]

LGTM 🚢