isEmpty typeguard strips types from empty arrays

[onebytegone]

Sample test:

it('keeps type information when checking for empty array', () => {
   const arr: string[] = [];

   if (isEmpty(arr)) {
      // Argument of type '"test"' is not assignable to parameter of type 'never'.ts(2345)
      arr.push('test');
   }

   expect(arr.length).to.strictlyEqual(1);
});