backend: Allow None as return from translate_uri()
backend: Allow None as return from translate_uri()

ali/mopidy,kingosticks/mopidy,SuperStarPL/mopidy,glogiotatidis/mopidy,ali/mopidy,hkariti/mopidy,swak/mopidy,vrs01/mopidy,kingosticks/mopidy,glogiotatidis/mopidy,mokieyue/mopidy,vrs01/mopidy,SuperStarPL/mopidy,mokieyue/mopidy,bacontext/mopidy,pacificIT/mopidy,hkariti/mopidy,ZenithDK/mopidy,mokieyue/mopidy,hkariti/mopidy,ZenithDK/mopidy,ZenithDK/mopidy,jmarsik/mopidy,rawdlite/mopidy,kingosticks/mopidy,diandiankan/mopidy,jodal/mopidy,mokieyue/mopidy,pacificIT/mopidy,jmarsik/mopidy,mopidy/mopidy,glogiotatidis/mopidy,jmarsik/mopidy,adamcik/mopidy,dbrgn/mopidy,quartz55/mopidy,jcass77/mopidy,quartz55/mopidy,hkariti/mopidy,swak/mopidy,jcass77/mopidy,glogiotatidis/mopidy,jodal/mopidy,bencevans/mopidy,ali/mopidy,bacontext/mopidy,mopidy/mopidy,bencevans/mopidy,swak/mopidy,dbrgn/mopidy,tkem/mopidy,dbrgn/mopidy,bacontext/mopidy,ZenithDK/mopidy,quartz55/mopidy,diandiankan/mopidy,tkem/mopidy,jmarsik/mopidy,diandiankan/mopidy,bencevans/mopidy,tkem/mopidy,swak/mopidy,ali/mopidy,jcass77/mopidy,rawdlite/mopidy,adamcik/mopidy,vrs01/mopidy,tkem/mopidy,SuperStarPL/mopidy,vrs01/mopidy,diandiankan/mopidy,mopidy/mopidy,rawdlite/mopidy,dbrgn/mopidy,quartz55/mopidy,bencevans/mopidy,bacontext/mopidy,pacificIT/mopidy,adamcik/mopidy,SuperStarPL/mopidy,pacificIT/mopidy,jodal/mopidy,rawdlite/mopidy