USYRA'S PROFILE

So, I'm a new game designer, and I'd like my main character to have three weapon types: axe, bow, and unarmed. I understand that I can go down to "Required Weapon" to make Axe skills usable only if they have an axe weapon equipped, or bow skills usable if they have a bow equipped. My question is if it's possible to make skills only available if no weapons are equipped.