Commandblock 1 (Wiederholen):
execute if items entity @a weapon.mainhand minecraft:crossbow[!charged_projectiles=[{id:"minecraft:arrow",count:1}]] run clear @a minecraft:arrow 1

Commandblock 2 (Verketten, Bedingt)
item replace entity @a weapon.mainhand with minecraft:crossbow[charged_projectiles=[{id:"minecraft:arrow",count:1}]]

Commandblock 3 (Verketten, Bedingt)
execute at @a run playsound minecraft:entity.wither.break_block master @a