Filtering out all data throw error

[turnerniles]

When providing filters that filter out all data, an error is thrown.

const dataArray = [
 ['name', 'gender', 'house', 'age'],
 ['Jon', 'm', 'Stark', 14],
 ['Arya', 'f', 'Stark', 10],
 ['Cersei', 'f', 'Baratheon', 38],
 ['Tywin', 'm', 'Lannister', 67],
 ['Tyrion', 'm', 'Lannister', 34],
 ['Joffrey', 'm', 'Baratheon', 18],
 ['Bran', 'm', 'Stark', 8],
 ['Jaime', 'm', 'Lannister', 32],
 ['Sansa', 'f', 'Stark', 12]
];

const pivot = new pivot(dataArray, ['gender'], [], 'age', 'count');
pivot.filter('gender', ['m', 'f'])