refactoring: add a defensive check for nullptr. rdar://48290050
refactoring: add a defensive check for nullptr. rdar://48290050

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