In comments, John Lawler wrote something that is important enough that it should be searchable here, so I am installing it as a "Community Wiki" answer:

Empty is one of the words that has a stative adjective form (The pot is empty), an inchoative verbal form (That pot empties fast), and a causative verbal form (He emptied that pot slowly) that all have the same shape. Unlike, for instance, full, which is only an adjective, but has related inchoative (The pot filled) and causative (He filled the pot). Or dead, which has a related inchoative die, and an unrelated causative kill. Zero derivation is quite common.