Tests if the topmost stack item's length is equal to zero.
NONE? will push
1 if the item's length is equal to zero,
It has a "sister" instruction of SOME?. Together they allow to express a concept of an optional value.
PumpkinDB>  NONE? 1 PumpkinDB>  NONE? 0
EmptyStack error if there is less than one items on the stack
works :  NONE?. works_1 :  NONE? NOT. empty_stack : [NONE?] TRY UNWRAP 0x04 EQUAL?.