Pillagers with empty hands may pick up non ominous banners

When a pillager does not hold any items, it may pick up a banner which is not ominous banner.

Steps to Reproduce:

1. Summon a pillager.
2. Use command /item to clear the crossbow it holds, or let it shoot until the durability runs out if you got the patience.
3. Throw any banner to the pillager.

Expected result: The pillager would not pick up the banners which are not ominous banners.

Observed result: The pillager would pick up any banners.

Plus: Items other than weapons in the general sense and banners are not accepted. So this should be unexpected.