fix Stylist::add_quirks_mode_stylesheet() to not panic when resources cannot be loaded
fix Stylist::add_quirks_mode_stylesheet() to not panic when resources cannot be loaded

avadacatavra/servo,cbrewster/servo,upsuper/servo,nnethercote/servo,boghison/servo,codemac/servo,jimberlage/servo,jgraham/servo,deokjinkim/servo,saneyuki/servo,rnestler/servo,jlegendary/servo,avadacatavra/servo,hyowon/servo,mattnenterprise/servo,pyfisch/servo,jdramani/servo,pyfisch/servo,nnethercote/servo,avadacatavra/servo,dhananjay92/servo,jdramani/servo,jimberlage/servo,DominoTree/servo,vks/servo,mattnenterprise/servo,pyfisch/servo,KiChjang/servo,jimberlage/servo,zhangjunlei26/servo,mt2d2/servo,eddyb/servo,s142857/servo,avadacatavra/servo,avadacatavra/servo,dagnir/servo,kindersung/servo,j3parker/servo,bjwbell/servo,nick-thompson/servo,paulrouget/servo,rixrix/servo,cbrewster/servo,upsuper/servo,runarberg/servo,zhangjunlei26/servo,steveklabnik/servo,mattnenterprise/servo,rnestler/servo,akosel/servo,codemac/servo,brendandahl/servo,notriddle/servo,emilio/servo,ConnorGBrewster/servo,tempbottle/servo,caldwell/servo,emilio/servo,mattnenterprise/servo,s142857/servo,meh/servo,emilio/servo,boghison/servo,aweinstock314/servo,youprofit/servo,GyrosOfWar/servo,s142857/servo,paulrouget/servo,upsuper/servo,KiChjang/servo,samfoo/servo,dvberkel/servo,cbrewster/servo,fiji-flo/servo,samfoo/servo,pyfisch/servo,cbrewster/servo,ryancanhelpyou/servo,DominoTree/servo,s142857/servo,j3parker/servo,walac/servo,tempbottle/servo,dvberkel/servo,peterjoel/servo,brendandahl/servo,j3parker/servo,KiChjang/servo,CJ8664/servo,dsandeephegde/servo,eddyb/servo,caldwell/servo,hyowon/servo,dvberkel/servo,ConnorGBrewster/servo,huonw/servo,rnestler/servo,rixrix/servo,mbrubeck/servo,anthgur/servo,notriddle/servo,WriterOfAlicrow/servo,jlegendary/servo,deokjinkim/servo,upsuper/servo,caldwell/servo,jdramani/servo,vks/servo,RenaudParis/servo,ConnorGBrewster/servo,tschneidereit/servo,jimberlage/servo,anthgur/servo,thiagopnts/servo,canaltinova/servo,sadmansk/servo,saneyuki/servo,ryancanhelpyou/servo,zentner-kyle/servo,GreenRecycleBin/servo,pyfisch/servo,peterjoel/servo,youprofit/servo,peterjoel/servo,anthgur/servo,karlito40/servo,szeged/servo,runarberg/servo,nerith/servo,nrc/servo,jgraham/servo,dhananjay92/servo,huonw/servo,dvberkel/servo,nerith/servo,larsbergstrom/servo,splav/servo,cbrewster/servo,dsandeephegde/servo,mdibaiee/servo,walac/servo,fiji-flo/servo,rixrix/servo,dhananjay92/servo,pgonda/servo,tempbottle/servo,rixrix/servo,aidanhs/servo,A-deLuna/servo,larsbergstrom/servo,GyrosOfWar/servo,wartman4404/servo,akosel/servo,tafia/servo,zentner-kyle/servo,huonw/servo,mattnenterprise/servo,wartman4404/servo,karlito40/servo,karlito40/servo,mbrubeck/servo,thiagopnts/servo,jgraham/servo,nerith/servo,saratang/servo,kindersung/servo,wartman4404/servo,jimberlage/servo,nick-thompson/servo,thiagopnts/servo,tempbottle/servo,SimonSapin/servo,GreenRecycleBin/servo,aweinstock314/servo,youprofit/servo,brendandahl/servo,runarberg/servo,jlegendary/servo,nrc/servo,huonw/servo,mdibaiee/servo,splav/servo,saneyuki/servo,KiChjang/servo,peterjoel/servo,peterjoel/servo,AnthonyBroadCrawford/servo,GreenRecycleBin/servo,saratang/servo,pyecs/servo,akosel/servo,sadmansk/servo,nick-thompson/servo,notriddle/servo,karlito40/servo,SimonSapin/servo,mbrubeck/servo,nnethercote/servo,meh/servo,upsuper/servo,zhangjunlei26/servo,pyecs/servo,dvberkel/servo,saneyuki/servo,notriddle/servo,dsandeephegde/servo,szeged/servo,meh/servo,samfoo/servo,runarberg/servo,dati91/servo,WriterOfAlicrow/servo,fiji-flo/servo,sadmansk/servo,saneyuki/servo,steveklabnik/servo,dagnir/servo,sadmansk/servo,aweinstock314/servo,eddyb/servo,pyecs/servo,larsbergstrom/servo,pyecs/servo,tempbottle/servo,brendandahl/servo,dati91/servo,deokjinkim/servo,WriterOfAlicrow/servo,rentongzhang/servo,aidanhs/servo,nnethercote/servo,jimberlage/servo,notriddle/servo,peterjoel/servo,szeged/servo,rnestler/servo,ryancanhelpyou/servo,hyowon/servo,deokjinkim/servo,saneyuki/servo,pyfisch/servo,nnethercote/servo,jdramani/servo,zentner-kyle/servo,vks/servo,CJ8664/servo,kindersung/servo,mdibaiee/servo,g-k/servo,tafia/servo,KiChjang/servo,cbrewster/servo,dati91/servo,dhananjay92/servo,walac/servo,saratang/servo,deokjinkim/servo,kindersung/servo,jdramani/servo,sadmansk/servo,hyowon/servo,tschneidereit/servo,WriterOfAlicrow/servo,SimonSapin/servo,RenaudParis/servo,nerith/servo,bjwbell/servo,ryancanhelpyou/servo,sadmansk/servo,larsbergstrom/servo,bjwbell/servo,bjwbell/servo,emilio/servo,s142857/servo,pgonda/servo,emilio/servo,szeged/servo,codemac/servo,emilio/servo,tschneidereit/servo,meh/servo,eddyb/servo,codemac/servo,dvberkel/servo,SimonSapin/servo,deokjinkim/servo,GreenRecycleBin/servo,zhangjunlei26/servo,AnthonyBroadCrawford/servo,jdramani/servo,fiji-flo/servo,brendandahl/servo,zentner-kyle/servo,GyrosOfWar/servo,fiji-flo/servo,peterjoel/servo,meh/servo,dati91/servo,CJ8664/servo,pyfisch/servo,akosel/servo,j3parker/servo,boghison/servo,DominoTree/servo,dsandeephegde/servo,pgonda/servo,deokjinkim/servo,larsbergstrom/servo,fiji-flo/servo,pyfisch/servo,notriddle/servo,pgonda/servo,steveklabnik/servo,A-deLuna/servo,mbrubeck/servo,fiji-flo/servo,nick-thompson/servo,dagnir/servo,mdibaiee/servo,rixrix/servo,aidanhs/servo,aweinstock314/servo,dsandeephegde/servo,nrc/servo,GreenRecycleBin/servo,pyfisch/servo,caldwell/servo,cbrewster/servo,larsbergstrom/servo,jgraham/servo,samfoo/servo,KiChjang/servo,steveklabnik/servo,thiagopnts/servo,larsbergstrom/servo,mbrubeck/servo,mdibaiee/servo,rentongzhang/servo,saratang/servo,tafia/servo,RenaudParis/servo,paulrouget/servo,tschneidereit/servo,canaltinova/servo,saneyuki/servo,CJ8664/servo,aidanhs/servo,dagnir/servo,steveklabnik/servo,GreenRecycleBin/servo,GreenRecycleBin/servo,szeged/servo,splav/servo,mattnenterprise/servo,sadmansk/servo,A-deLuna/servo,codemac/servo,j3parker/servo,j3parker/servo,dhananjay92/servo,CJ8664/servo,notriddle/servo,AnthonyBroadCrawford/servo,nick-thompson/servo,zentner-kyle/servo,mt2d2/servo,saneyuki/servo,boghison/servo,aidanhs/servo,splav/servo,paulrouget/servo,rnestler/servo,nnethercote/servo,dagnir/servo,RenaudParis/servo,saratang/servo,notriddle/servo,dati91/servo,walac/servo,saneyuki/servo,ryancanhelpyou/servo,RenaudParis/servo,avadacatavra/servo,kindersung/servo,eddyb/servo,rentongzhang/servo,nrc/servo,zhangjunlei26/servo,emilio/servo,g-k/servo,notriddle/servo,dagnir/servo,saratang/servo,mt2d2/servo,RenaudParis/servo,jdramani/servo,paulrouget/servo,A-deLuna/servo,runarberg/servo,splav/servo,avadacatavra/servo,aidanhs/servo,samfoo/servo,szeged/servo,GreenRecycleBin/servo,WriterOfAlicrow/servo,rentongzhang/servo,dvberkel/servo,GyrosOfWar/servo,steveklabnik/servo,jlegendary/servo,KiChjang/servo,jgraham/servo,canaltinova/servo,mbrubeck/servo,mattnenterprise/servo,nnethercote/servo,bjwbell/servo,anthgur/servo,CJ8664/servo,karlito40/servo,aweinstock314/servo,thiagopnts/servo,canaltinova/servo,ConnorGBrewster/servo,brendandahl/servo,dhananjay92/servo,wartman4404/servo,saneyuki/servo,g-k/servo,codemac/servo,karlito40/servo,hyowon/servo,ryancanhelpyou/servo,jlegendary/servo,huonw/servo,AnthonyBroadCrawford/servo,mt2d2/servo,nerith/servo,paulrouget/servo,KiChjang/servo,jimberlage/servo,tschneidereit/servo,boghison/servo,splav/servo,hyowon/servo,emilio/servo,splav/servo,anthgur/servo,pyecs/servo,cbrewster/servo,kindersung/servo,youprofit/servo,kindersung/servo,GyrosOfWar/servo,thiagopnts/servo,jgraham/servo,eddyb/servo,tafia/servo,rentongzhang/servo,upsuper/servo,ConnorGBrewster/servo,g-k/servo,ryancanhelpyou/servo,canaltinova/servo,eddyb/servo,g-k/servo,huonw/servo,tempbottle/servo,pyecs/servo,dhananjay92/servo,mdibaiee/servo,jimberlage/servo,mt2d2/servo,dsandeephegde/servo,caldwell/servo,nerith/servo,peterjoel/servo,DominoTree/servo,A-deLuna/servo,brendandahl/servo,dati91/servo,samfoo/servo,GyrosOfWar/servo,akosel/servo,GreenRecycleBin/servo,rixrix/servo,AnthonyBroadCrawford/servo,DominoTree/servo,walac/servo,anthgur/servo,anthgur/servo,WriterOfAlicrow/servo,aweinstock314/servo,anthgur/servo,A-deLuna/servo,SimonSapin/servo,akosel/servo,splav/servo,tschneidereit/servo,DominoTree/servo,SimonSapin/servo,vks/servo,youprofit/servo,zentner-kyle/servo,eddyb/servo,pgonda/servo,rnestler/servo,bjwbell/servo,DominoTree/servo,rixrix/servo,avadacatavra/servo,tafia/servo,zentner-kyle/servo,samfoo/servo,mdibaiee/servo,thiagopnts/servo,boghison/servo,j3parker/servo,walac/servo,mt2d2/servo,splav/servo,ConnorGBrewster/servo,jgraham/servo,dati91/servo,szeged/servo,nerith/servo,dagnir/servo,bjwbell/servo,AnthonyBroadCrawford/servo,wartman4404/servo,aidanhs/servo,huonw/servo,mbrubeck/servo,jlegendary/servo,zhangjunlei26/servo,DominoTree/servo,mbrubeck/servo,zhangjunlei26/servo,nick-thompson/servo,DominoTree/servo,pyfisch/servo,szeged/servo,canaltinova/servo,youprofit/servo,emilio/servo,KiChjang/servo,peterjoel/servo,vks/servo,paulrouget/servo,fiji-flo/servo,paulrouget/servo,CJ8664/servo,A-deLuna/servo,codemac/servo,SimonSapin/servo,vks/servo,nrc/servo,dsandeephegde/servo,wartman4404/servo,splav/servo,nick-thompson/servo,s142857/servo,rentongzhang/servo,tschneidereit/servo,karlito40/servo,pyecs/servo,caldwell/servo,CJ8664/servo,sadmansk/servo,upsuper/servo,vks/servo,rnestler/servo,zhangjunlei26/servo,SimonSapin/servo,paulrouget/servo,nnethercote/servo,rixrix/servo,akosel/servo,caldwell/servo,pgonda/servo,pgonda/servo,g-k/servo,szeged/servo,nrc/servo,zhangjunlei26/servo,meh/servo,GyrosOfWar/servo,peterjoel/servo,steveklabnik/servo,ConnorGBrewster/servo,hyowon/servo,canaltinova/servo,saratang/servo,tafia/servo,emilio/servo,KiChjang/servo,boghison/servo,s142857/servo,DominoTree/servo,thiagopnts/servo,dati91/servo,aweinstock314/servo,ConnorGBrewster/servo,wartman4404/servo,youprofit/servo,nrc/servo,meh/servo,AnthonyBroadCrawford/servo,rentongzhang/servo,runarberg/servo,canaltinova/servo,mattnenterprise/servo,walac/servo,tempbottle/servo,dsandeephegde/servo,runarberg/servo,jimberlage/servo,larsbergstrom/servo,notriddle/servo,rixrix/servo,larsbergstrom/servo,RenaudParis/servo,larsbergstrom/servo,szeged/servo,nnethercote/servo,rnestler/servo,mt2d2/servo,WriterOfAlicrow/servo,g-k/servo,paulrouget/servo,nnethercote/servo,jlegendary/servo,tafia/servo,upsuper/servo