Fix issue with dropping constraint that does not exist
Fix issue with dropping constraint that does not exist

dunknicoll/phinx,PinZhang/phinx,aCodify/phinx,t1gor/phinx,boedy/phinx,aCodify/phinx,berarma/phinx,kevbaldwyn/phinx,daniel-gomes-sociomantic/phinx,laurin1/phinx,dancryer/phinx,ikagawa/phinx,boedy/phinx,k10r/phinx,BambooHR/phinx-mt,angelorighi/phinx,dankempster/phinx,lornajane/phinx,vitormattos/phinx,rquadling/phinx,castamir/phinx,Thamrongsak/phinx,curtisgibby/phinx,robmorgan/phinx,DeltaPHP/phinx,stevemarksmonii/phinx,channelgrabber/phinx,igormx/phinx,Stene3/phinx,kamioftea/phinx,lzpfmh/phinx,jimdoescode/phinx,courtney-miles/phinx,gnugat/phinx,gerkirill/phinx,HavokInspiration/phinx