Adding parameters with multiple selection

Please help with Paginated report. Report builder is powered by data from the power bi web dataset. The dataset is Azure Analysis Servers. I can't manage to set all fields selected by default or the option to select the default "null" on one of the parameters. If the user would like to select data from this field, I want him to be able to select multiple options, not just one.

How to do it?

The "EAN" field is just the parameter it should be as a multiple choice filter with "all fields" selected by default Below is the dataset query that is in the report builder:

DEFINE VAR __DS0Core = 
	SUMMARIZECOLUMNS(
		ROLLUPADDISSUBTOTAL(
			ROLLUPGROUP(
				'TableA'[Dodane przez],
				'TableA'[Kolekcja],
				'TableA'[Asortyment],
				'TableA'[Department],
				'TableA'[Grupa towarowa-kategoria],
				'TableA'[Płeć],
				'TableA'[Typ],
				'TableA'[Podtyp],
				'TableA'[Wejście],
				'TableA'[Sezon],
				'TableA'[Rodzaj pakowania],
				'TableA'[RepeatOrder],
				'TableA'[Nazwa modelu],
				'TableA'[EAN],
				'TableA'[Season]
			), "IsGrandTotalRowTotal"
		),
		"SumZaliczka__", CALCULATE(SUM('TableB'[Zaliczka %])),
		"SumIlość_dni_do_odroczenia", CALCULATE(SUM('TableB'[Ilość dni do odroczenia]))
	

EVALUATE
	__DS0Core