discogs: tweak pruning of empty candidate albums
discogs: tweak pruning of empty candidate albums

ibmibmibm/beets,pkess/beets,xsteadfastx/beets,madmouser1/beets,beetbox/beets,MyTunesFreeMusic/privacy-policy,jackwilsdon/beets,mosesfistos1/beetbox,beetbox/beets,sampsyo/beets,ibmibmibm/beets,Kraymer/beets,ibmibmibm/beets,Kraymer/beets,jackwilsdon/beets,jackwilsdon/beets,MyTunesFreeMusic/privacy-policy,Kraymer/beets,shamangeorge/beets,SusannaMaria/beets,MyTunesFreeMusic/privacy-policy,madmouser1/beets,shamangeorge/beets,madmouser1/beets,mosesfistos1/beetbox,sampsyo/beets,Kraymer/beets,sampsyo/beets,shamangeorge/beets,beetbox/beets,SusannaMaria/beets,shamangeorge/beets,SusannaMaria/beets,lengtche/beets,mosesfistos1/beetbox,beetbox/beets,lengtche/beets,mosesfistos1/beetbox,xsteadfastx/beets,xsteadfastx/beets,madmouser1/beets,SusannaMaria/beets,xsteadfastx/beets,ibmibmibm/beets,jackwilsdon/beets,lengtche/beets,lengtche/beets,artemutin/beets,MyTunesFreeMusic/privacy-policy,pkess/beets,sampsyo/beets,artemutin/beets,artemutin/beets,pkess/beets,pkess/beets,artemutin/beets