roller: check for existence in resend nonce
=/ cards=(list card) (send-roll:do address nonce)
=? sending
?& ?=(~ cards)
+ (has:ors:dice sending [address nonce])
=(0 (lent txs:(got:ors:dice sending [address nonce])))
==
~& > "empty sending, removing {<[nonce address]>}"
