Fix definededness test in merge_boxes
Fix definededness test in merge_boxes

kgnk/Halide,mcanthony/Halide,ayanazmat/Halide,fengzhyuan/Halide,rodrigob/Halide,jiawen/Halide,delcypher/Halide,ayanazmat/Halide,mcanthony/Halide,rodrigob/Halide,damienfir/Halide,ronen/Halide,myrtleTree33/Halide,tdenniston/Halide,psuriana/Halide,kgnk/Halide,adasworks/Halide,kenkuang1213/Halide,aam/Halide,delcypher/Halide,tdenniston/Halide,fengzhyuan/Halide,mcanthony/Halide,psuriana/Halide,jiawen/Halide,aam/Halide,aam/Halide,fengzhyuan/Halide,psuriana/Halide,adasworks/Halide,jiawen/Halide,jiawen/Halide,delcypher/Halide,mcanthony/Halide,kenkuang1213/Halide,smxlong/Halide,damienfir/Halide,ronen/Halide,delcypher/Halide,mcanthony/Halide,adasworks/Halide,fengzhyuan/Halide,dougkwan/Halide,myrtleTree33/Halide,ayanazmat/Halide,lglucin/Halide,kenkuang1213/Halide,dan-tull/Halide,dan-tull/Halide,ayanazmat/Halide,myrtleTree33/Halide,gchauras/Halide,kgnk/Halide,kgnk/Halide,dan-tull/Halide,smxlong/Halide,tdenniston/Halide,fengzhyuan/Halide,kenkuang1213/Halide,delcypher/Halide,gchauras/Halide,ayanazmat/Halide,lglucin/Halide,ronen/Halide,adasworks/Halide,kgnk/Halide,aam/Halide,ayanazmat/Halide,smxlong/Halide,lglucin/Halide,jiawen/Halide,smxlong/Halide,jiawen/Halide,fengzhyuan/Halide,rodrigob/Halide,ronen/Halide,tdenniston/Halide,gchauras/Halide,adasworks/Halide,tdenniston/Halide,psuriana/Halide,ronen/Halide,psuriana/Halide,adasworks/Halide,fengzhyuan/Halide,kenkuang1213/Halide,myrtleTree33/Halide,smxlong/Halide,damienfir/Halide,myrtleTree33/Halide,kgnk/Halide,damienfir/Halide,tdenniston/Halide,gchauras/Halide,smxlong/Halide,ayanazmat/Halide,rodrigob/Halide,aam/Halide,smxlong/Halide,adasworks/Halide,gchauras/Halide,mcanthony/Halide,rodrigob/Halide,tdenniston/Halide,mcanthony/Halide,delcypher/Halide,delcypher/Halide,dougkwan/Halide,psuriana/Halide,kgnk/Halide,lglucin/Halide,fengzhyuan/Halide,dougkwan/Halide,aam/Halide,ronen/Halide,dougkwan/Halide,rodrigob/Halide,kgnk/Halide,lglucin/Halide,dougkwan/Halide,psuriana/Halide,dougkwan/Halide,adasworks/Halide,ayanazmat/Halide,myrtleTree33/Halide,ronen/Halide,rodrigob/Halide,lglucin/Halide,myrtleTree33/Halide,damienfir/Halide,dan-tull/Halide,dan-tull/Halide,lglucin/Halide,kenkuang1213/Halide,kenkuang1213/Halide,rodrigob/Halide,tdenniston/Halide,damienfir/Halide,aam/Halide,ronen/Halide,mcanthony/Halide,gchauras/Halide,smxlong/Halide,dougkwan/Halide,damienfir/Halide,dan-tull/Halide,dan-tull/Halide,delcypher/Halide,myrtleTree33/Halide,dan-tull/Halide,jiawen/Halide,kenkuang1213/Halide,damienfir/Halide,dougkwan/Halide