Fix handling of null relative references in RemoteRef.
Fix handling of null relative references in RemoteRef.

aschwaighofer/swift,gribozavr/swift,gregomni/swift,hooman/swift,glessard/swift,roambotics/swift,glessard/swift,stephentyrone/swift,nathawes/swift,glessard/swift,CodaFi/swift,jmgc/swift,devincoughlin/swift,airspeedswift/swift,JGiola/swift,airspeedswift/swift,jckarter/swift,airspeedswift/swift,nathawes/swift,lorentey/swift,hooman/swift,jckarter/swift,harlanhaskins/swift,ahoppen/swift,devincoughlin/swift,xwu/swift,jckarter/swift,atrick/swift,karwa/swift,rudkx/swift,benlangmuir/swift,parkera/swift,glessard/swift,lorentey/swift,sschiau/swift,gribozavr/swift,parkera/swift,harlanhaskins/swift,parkera/swift,jmgc/swift,parkera/swift,JGiola/swift,apple/swift,harlanhaskins/swift,gribozavr/swift,parkera/swift,lorentey/swift,parkera/swift,xwu/swift,gribozavr/swift,aschwaighofer/swift,apple/swift,nathawes/swift,allevato/swift,ahoppen/swift,aschwaighofer/swift,allevato/swift,allevato/swift,rudkx/swift,sschiau/swift,gregomni/swift,airspeedswift/swift,gribozavr/swift,harlanhaskins/swift,CodaFi/swift,gribozavr/swift,roambotics/swift,gregomni/swift,roambotics/swift,karwa/swift,sschiau/swift,rudkx/swift,atrick/swift,sschiau/swift,atrick/swift,ahoppen/swift,JGiola/swift,roambotics/swift,devincoughlin/swift,CodaFi/swift,hooman/swift,apple/swift,tkremenek/swift,ahoppen/swift,jmgc/swift,tkremenek/swift,atrick/swift,apple/swift,gregomni/swift,glessard/swift,rudkx/swift,harlanhaskins/swift,hooman/swift,tkremenek/swift,sschiau/swift,JGiola/swift,devincoughlin/swift,apple/swift,rudkx/swift,parkera/swift,gregomni/swift,sschiau/swift,airspeedswift/swift,karwa/swift,tkremenek/swift,gribozavr/swift,JGiola/swift,aschwaighofer/swift,jmgc/swift,CodaFi/swift,hooman/swift,hooman/swift,gregomni/swift,devincoughlin/swift,aschwaighofer/swift,stephentyrone/swift,gribozavr/swift,karwa/swift,karwa/swift,benlangmuir/swift,xwu/swift,devincoughlin/swift,sschiau/swift,allevato/swift,stephentyrone/swift,rudkx/swift,apple/swift,harlanhaskins/swift,parkera/swift,stephentyrone/swift,roambotics/swift,lorentey/swift,hooman/swift,ahoppen/swift,CodaFi/swift,jckarter/swift,karwa/swift,jckarter/swift,glessard/swift,aschwaighofer/swift,roambotics/swift,harlanhaskins/swift,nathawes/swift,benlangmuir/swift,devincoughlin/swift,aschwaighofer/swift,JGiola/swift,xwu/swift,nathawes/swift,atrick/swift,jckarter/swift,devincoughlin/swift,stephentyrone/swift,airspeedswift/swift,lorentey/swift,benlangmuir/swift,benlangmuir/swift,tkremenek/swift,stephentyrone/swift,karwa/swift,jmgc/swift,xwu/swift,CodaFi/swift,benlangmuir/swift,tkremenek/swift,allevato/swift,airspeedswift/swift,jmgc/swift,atrick/swift,nathawes/swift,xwu/swift,jmgc/swift,lorentey/swift,xwu/swift,ahoppen/swift,sschiau/swift,karwa/swift,allevato/swift,nathawes/swift,CodaFi/swift,allevato/swift,jckarter/swift,lorentey/swift,stephentyrone/swift,lorentey/swift,tkremenek/swift