Unable to buy mystery skin despite owning all champions

Preventing people with fewer than ten champions in the skin pool from purchasing skins was intended to keep people from gaming the system by only buying a couple champions and then having an increased chance to get an extremely expensive skin.

However, people that own all the champions clearly aren't trying to game the system in this way, so they should not be prevented from purchasing mystery skins.

Please allow people that own all champions to always be able to purchase mystery skins, no matter how few are remaining to purchase.