convert: Fix problem with "threads" config option
convert: Fix problem with "threads" config option

jayme-github/beets,m-urban/beets,imsparsh/beets,xsteadfastx/beets,imsparsh/beets,parapente/beets,xsteadfastx/beets,ibmibmibm/beets,drm00/beets,jackwilsdon/beets,jmwatte/beets,mathstuf/beets,MyTunesFreeMusic/privacy-policy,shanemikel/beets,untitaker/beets,m-urban/beets,pkess/beets,mathstuf/beets,Kraymer/beets,YetAnotherNerd/beets,untitaker/beets,madmouser1/beets,dfc/beets,swt30/beets,imsparsh/beets,asteven/beets,randybias/beets,marcuskrahl/beets,beetbox/beets,swt30/beets,jayme-github/beets,PierreRust/beets,parapente/beets,PierreRust/beets,Freso/beets,mried/beets,pkess/beets,artemutin/beets,artemutin/beets,gabrielaraujof/beets,asteven/beets,jackwilsdon/beets,sampsyo/beets,jcoady9/beets,YetAnotherNerd/beets,moodboom/beets,xsteadfastx/beets,parapente/beets,diego-plan9/beets,Andypsamp/CODfinalJUNIT,LordSputnik/beets,Dishwishy/beets,jmwatte/beets,jackwilsdon/beets,pkess/beets,Wen777/beets,LordSputnik/beets,SusannaMaria/beets,mosesfistos1/beetbox,Andypsamp/CODfinalJUNIT,ttsda/beets,MyTunesFreeMusic/privacy-policy,krig/beets,lightwang1/beets,PierreRust/beets,Andypsamp/CODjunit,mosesfistos1/beetbox,marcuskrahl/beets,bj-yinyan/beets,andremiller/beets,drm00/beets,asteven/beets,jmwatte/beets,lengtche/beets,krig/beets,Andypsamp/CODfinalJUNIT,jmwatte/beets,beetbox/beets,moodboom/beets,drm00/beets,untitaker/beets,multikatt/beets,madmouser1/beets,asteven/beets,jbaiter/beets,ruippeixotog/beets,artemutin/beets,gabrielaraujof/beets,mathstuf/beets,moodboom/beets,sampsyo/beets,kareemallen/beets,lightwang1/beets,diego-plan9/beets,YetAnotherNerd/beets,Andypsamp/CODjunit,tima/beets,ttsda/beets,beetbox/beets,xsteadfastx/beets,LordSputnik/beets,lengtche/beets,PierreRust/beets,SusannaMaria/beets,ttsda/beets,YetAnotherNerd/beets,tima/beets,lightwang1/beets,gabrielaraujof/beets,pdf/beets,mried/beets,kelvinhammond/beets,Wen777/beets,andremiller/beets,MyTunesFreeMusic/privacy-policy,kelvinhammond/beets,Andypsamp/CODfinalJUNIT,shamangeorge/beets,untitaker/beets,lengtche/beets,kareemallen/beets,Freso/beets,arabenjamin/beets,mathstuf/beets,dfc/beets,shamangeorge/beets,dfc/beets,shanemikel/beets,m-urban/beets,marcuskrahl/beets,Kraymer/beets,SusannaMaria/beets,randybias/beets,swt30/beets,parapente/beets,artemutin/beets,madmouser1/beets,Andypsamp/CODjunit,mosesfistos1/beetbox,arabenjamin/beets,Kraymer/beets,Dishwishy/beets,tima/beets,jbaiter/beets,diego-plan9/beets,Freso/beets,bj-yinyan/beets,kelvinhammond/beets,Wen777/beets,pkess/beets,Kraymer/beets,krig/beets,ttsda/beets,jackwilsdon/beets,bj-yinyan/beets,jcoady9/beets,pdf/beets,lightwang1/beets,LordSputnik/beets,shanemikel/beets,sampsyo/beets,ibmibmibm/beets,shamangeorge/beets,drm00/beets,shamangeorge/beets,m-urban/beets,Andypsamp/CODfinalJUNIT,MyTunesFreeMusic/privacy-policy,dfc/beets,mried/beets,diego-plan9/beets,ruippeixotog/beets,multikatt/beets,arabenjamin/beets,multikatt/beets,mried/beets,SusannaMaria/beets,mosesfistos1/beetbox,moodboom/beets,Dishwishy/beets,gabrielaraujof/beets,Andypsamp/CODjunit,jcoady9/beets,sadatay/beets,swt30/beets,sadatay/beets,randybias/beets,beetbox/beets,Freso/beets,imsparsh/beets,kareemallen/beets,ruippeixotog/beets,kareemallen/beets,marcuskrahl/beets,ibmibmibm/beets,randybias/beets,andremiller/beets,madmouser1/beets,tima/beets,lengtche/beets,sadatay/beets,Dishwishy/beets,shanemikel/beets,sampsyo/beets,jcoady9/beets,kelvinhammond/beets,ibmibmibm/beets,Andypsamp/CODjunit,ruippeixotog/beets,arabenjamin/beets,sadatay/beets,bj-yinyan/beets,multikatt/beets