[mempool] always assert coin spent
[mempool] always assert coin spent

This is an extremely cheap function (just checks that the coin CTxOut
isn't null) that doesn't need to be gated on check_ratio.

pataquets/namecoin-core,fujicoin/fujicoin,bitcoin/bitcoin,jambolo/bitcoin,lateminer/bitcoin,GroestlCoin/bitcoin,namecoin/namecoin-core,fujicoin/fujicoin,jambolo/bitcoin,namecoin/namecore,namecoin/namecore,domob1812/bitcoin,andreaskern/bitcoin,AkioNak/bitcoin,Xekyo/bitcoin,bitcoin/bitcoin,GroestlCoin/GroestlCoin,bitcoinknots/bitcoin,mm-s/bitcoin,sstone/bitcoin,particl/particl-core,pataquets/namecoin-core,jamesob/bitcoin,tecnovert/particl-core,sstone/bitcoin,domob1812/bitcoin,sipsorcery/bitcoin,achow101/bitcoin,particl/particl-core,sipsorcery/bitcoin,sipsorcery/bitcoin,tecnovert/particl-core,sipsorcery/bitcoin,instagibbs/bitcoin,namecoin/namecore,jambolo/bitcoin,instagibbs/bitcoin,namecoin/namecore,instagibbs/bitcoin,bitcoin/bitcoin,jlopp/statoshi,domob1812/namecore,sstone/bitcoin,achow101/bitcoin,pataquets/namecoin-core,dscotese/bitcoin,achow101/bitcoin,fujicoin/fujicoin,mruddy/bitcoin,pataquets/namecoin-core,sstone/bitcoin,namecoin/namecoin-core,kallewoof/bitcoin,dscotese/bitcoin,fanquake/bitcoin,GroestlCoin/GroestlCoin,tecnovert/particl-core,AkioNak/bitcoin,bitcoinsSG/bitcoin,Xekyo/bitcoin,namecoin/namecore,instagibbs/bitcoin,jlopp/statoshi,tecnovert/particl-core,bitcoin/bitcoin,andreaskern/bitcoin,AkioNak/bitcoin,AkioNak/bitcoin,andreaskern/bitcoin,ajtowns/bitcoin,domob1812/namecore,kallewoof/bitcoin,anditto/bitcoin,ajtowns/bitcoin,namecoin/namecoin-core,jlopp/statoshi,domob1812/namecore,GroestlCoin/GroestlCoin,fanquake/bitcoin,fujicoin/fujicoin,lateminer/bitcoin,domob1812/bitcoin,anditto/bitcoin,dscotese/bitcoin,mm-s/bitcoin,GroestlCoin/GroestlCoin,GroestlCoin/bitcoin,tecnovert/particl-core,achow101/bitcoin,bitcoinknots/bitcoin,lateminer/bitcoin,kallewoof/bitcoin,GroestlCoin/bitcoin,namecoin/namecoin-core,domob1812/namecore,GroestlCoin/bitcoin,ajtowns/bitcoin,GroestlCoin/GroestlCoin,lateminer/bitcoin,domob1812/namecore,AkioNak/bitcoin,sstone/bitcoin,dscotese/bitcoin,Xekyo/bitcoin,tecnovert/particl-core,kallewoof/bitcoin,fanquake/bitcoin,ajtowns/bitcoin,namecoin/namecore,jlopp/statoshi,mruddy/bitcoin,particl/particl-core,GroestlCoin/GroestlCoin,bitcoinknots/bitcoin,jamesob/bitcoin,particl/particl-core,namecoin/namecoin-core,domob1812/namecore,andreaskern/bitcoin,domob1812/bitcoin,dscotese/bitcoin,fujicoin/fujicoin,mruddy/bitcoin,andreaskern/bitcoin,bitcoinsSG/bitcoin,domob1812/bitcoin,jamesob/bitcoin,jlopp/statoshi,GroestlCoin/bitcoin,jamesob/bitcoin,sipsorcery/bitcoin,kallewoof/bitcoin,bitcoinsSG/bitcoin,Xekyo/bitcoin,AkioNak/bitcoin,instagibbs/bitcoin,fanquake/bitcoin,GroestlCoin/bitcoin,sipsorcery/bitcoin,mruddy/bitcoin,andreaskern/bitcoin,lateminer/bitcoin,mm-s/bitcoin,mm-s/bitcoin,Xekyo/bitcoin,fanquake/bitcoin,namecoin/namecoin-core,bitcoinsSG/bitcoin,bitcoinsSG/bitcoin,bitcoin/bitcoin,achow101/bitcoin,lateminer/bitcoin,anditto/bitcoin,fanquake/bitcoin,anditto/bitcoin,jambolo/bitcoin,bitcoinknots/bitcoin,bitcoinknots/bitcoin,fujicoin/fujicoin,bitcoinsSG/bitcoin,ajtowns/bitcoin,pataquets/namecoin-core,particl/particl-core,kallewoof/bitcoin,jamesob/bitcoin,anditto/bitcoin,mm-s/bitcoin,jambolo/bitcoin,Xekyo/bitcoin,mm-s/bitcoin,sstone/bitcoin,mruddy/bitcoin,instagibbs/bitcoin,achow101/bitcoin,particl/particl-core,jamesob/bitcoin,anditto/bitcoin,domob1812/bitcoin,jlopp/statoshi,bitcoin/bitcoin,pataquets/namecoin-core,ajtowns/bitcoin,jambolo/bitcoin,dscotese/bitcoin,mruddy/bitcoin