Show Null as Option in Parameter Linked to Field

I have a string parameter, which is show on the sheet with Style of “Dropdown - multiselect”. It is linked to a field in my dataset. That field has null values in the dataset, but in the parameter drop down, null does not show up. Is there a way to include a null option in the parameter dropdown?

Hi, we are working to enable null in the paramete drop down list. It will be soon available this year.