Add a protection when drawing a canvas from a ROOT file
Add a protection when drawing a canvas from a ROOT file

Prevent potential crash when drawing a canvas with the same name than a canvas already embedded in one of the browser's tab.
This should prevent the crash described in the Jira issue #ROOT-6088

Duraznos/root,nilqed/root,dfunke/root,thomaskeck/root,smarinac/root,buuck/root,satyarth934/root,agarciamontoro/root,veprbl/root,agarciamontoro/root,krafczyk/root,Y--/root,simonpf/root,arch1tect0r/root,vukasinmilosevic/root,satyarth934/root,gganis/root,pspe/root,sawenzel/root,vukasinmilosevic/root,vukasinmilosevic/root,BerserkerTroll/root,veprbl/root,krafczyk/root,lgiommi/root,sirinath/root,nilqed/root,thomaskeck/root,mkret2/root,perovic/root,georgtroska/root,beniz/root,davidlt/root,omazapa/root-old,Duraznos/root,arch1tect0r/root,omazapa/root,gbitzes/root,arch1tect0r/root,karies/root,krafczyk/root,arch1tect0r/root,buuck/root,lgiommi/root,omazapa/root-old,veprbl/root,Duraznos/root,sawenzel/root,smarinac/root,jrtomps/root,satyarth934/root,agarciamontoro/root,zzxuanyuan/root,bbockelm/root,mhuwiler/rootauto,Duraznos/root,davidlt/root,zzxuanyuan/root,buuck/root,thomaskeck/root,zzxuanyuan/root-compressor-dummy,perovic/root,gganis/root,perovic/root,mkret2/root,beniz/root,dfunke/root,arch1tect0r/root,omazapa/root,dfunke/root,dfunke/root,vukasinmilosevic/root,omazapa/root-old,Duraznos/root,pspe/root,sbinet/cxx-root,georgtroska/root,georgtroska/root,sbinet/cxx-root,smarinac/root,mhuwiler/rootauto,mattkretz/root,veprbl/root,abhinavmoudgil95/root,gbitzes/root,Y--/root,arch1tect0r/root,thomaskeck/root,nilqed/root,bbockelm/root,esakellari/my_root_for_test,evgeny-boger/root,satyarth934/root,smarinac/root,smarinac/root,buuck/root,evgeny-boger/root,esakellari/my_root_for_test,zzxuanyuan/root,perovic/root,agarciamontoro/root,nilqed/root,jrtomps/root,georgtroska/root,Y--/root,beniz/root,buuck/root,esakellari/root,lgiommi/root,mkret2/root,agarciamontoro/root,CristinaCristescu/root,gganis/root,sawenzel/root,sawenzel/root,olifre/root,davidlt/root,vukasinmilosevic/root,smarinac/root,beniz/root,sirinath/root,krafczyk/root,karies/root,mhuwiler/rootauto,pspe/root,georgtroska/root,bbockelm/root,abhinavmoudgil95/root,evgeny-boger/root,abhinavmoudgil95/root,mhuwiler/rootauto,beniz/root,lgiommi/root,pspe/root,mkret2/root,sawenzel/root,jrtomps/root,sirinath/root,davidlt/root,bbockelm/root,gbitzes/root,krafczyk/root,esakellari/my_root_for_test,jrtomps/root,veprbl/root,nilqed/root,evgeny-boger/root,Duraznos/root,buuck/root,abhinavmoudgil95/root,omazapa/root,gganis/root,sbinet/cxx-root,beniz/root,agarciamontoro/root,dfunke/root,zzxuanyuan/root-compressor-dummy,krafczyk/root,esakellari/my_root_for_test,sirinath/root,olifre/root,esakellari/root,mhuwiler/rootauto,zzxuanyuan/root,esakellari/root,BerserkerTroll/root,root-mirror/root,smarinac/root,zzxuanyuan/root,omazapa/root-old,esakellari/root,buuck/root,perovic/root,dfunke/root,thomaskeck/root,evgeny-boger/root,root-mirror/root,georgtroska/root,gbitzes/root,satyarth934/root,Y--/root,thomaskeck/root,olifre/root,vukasinmilosevic/root,bbockelm/root,buuck/root,mhuwiler/rootauto,dfunke/root,CristinaCristescu/root,veprbl/root,sbinet/cxx-root,arch1tect0r/root,karies/root,bbockelm/root,simonpf/root,simonpf/root,satyarth934/root,sawenzel/root,sirinath/root,sirinath/root,CristinaCristescu/root,vukasinmilosevic/root,omazapa/root,Y--/root,zzxuanyuan/root,nilqed/root,veprbl/root,esakellari/root,root-mirror/root,0x0all/ROOT,sawenzel/root,mkret2/root,CristinaCristescu/root,esakellari/root,zzxuanyuan/root,sawenzel/root,BerserkerTroll/root,mattkretz/root,evgeny-boger/root,krafczyk/root,sawenzel/root,mkret2/root,perovic/root,karies/root,Y--/root,simonpf/root,olifre/root,zzxuanyuan/root,zzxuanyuan/root-compressor-dummy,omazapa/root-old,0x0all/ROOT,mhuwiler/rootauto,mkret2/root,karies/root,veprbl/root,buuck/root,simonpf/root,bbockelm/root,pspe/root,sbinet/cxx-root,abhinavmoudgil95/root,abhinavmoudgil95/root,satyarth934/root,krafczyk/root,lgiommi/root,sawenzel/root,Y--/root,esakellari/root,simonpf/root,root-mirror/root,karies/root,root-mirror/root,mhuwiler/rootauto,davidlt/root,mhuwiler/rootauto,beniz/root,pspe/root,CristinaCristescu/root,gganis/root,krafczyk/root,perovic/root,zzxuanyuan/root-compressor-dummy,esakellari/my_root_for_test,sirinath/root,olifre/root,esakellari/my_root_for_test,CristinaCristescu/root,perovic/root,georgtroska/root,agarciamontoro/root,abhinavmoudgil95/root,satyarth934/root,dfunke/root,gbitzes/root,zzxuanyuan/root-compressor-dummy,veprbl/root,mattkretz/root,agarciamontoro/root,Duraznos/root,nilqed/root,mattkretz/root,smarinac/root,BerserkerTroll/root,omazapa/root-old,gganis/root,veprbl/root,olifre/root,0x0all/ROOT,smarinac/root,krafczyk/root,gbitzes/root,buuck/root,thomaskeck/root,bbockelm/root,evgeny-boger/root,dfunke/root,esakellari/my_root_for_test,satyarth934/root,vukasinmilosevic/root,BerserkerTroll/root,jrtomps/root,0x0all/ROOT,bbockelm/root,esakellari/my_root_for_test,thomaskeck/root,sbinet/cxx-root,gganis/root,evgeny-boger/root,BerserkerTroll/root,olifre/root,zzxuanyuan/root-compressor-dummy,vukasinmilosevic/root,zzxuanyuan/root,perovic/root,BerserkerTroll/root,sirinath/root,omazapa/root-old,dfunke/root,satyarth934/root,omazapa/root,georgtroska/root,beniz/root,esakellari/my_root_for_test,Duraznos/root,root-mirror/root,davidlt/root,vukasinmilosevic/root,0x0all/ROOT,lgiommi/root,omazapa/root,zzxuanyuan/root-compressor-dummy,sbinet/cxx-root,davidlt/root,esakellari/my_root_for_test,gganis/root,bbockelm/root,zzxuanyuan/root-compressor-dummy,sirinath/root,thomaskeck/root,0x0all/ROOT,davidlt/root,0x0all/ROOT,krafczyk/root,esakellari/root,karies/root,satyarth934/root,jrtomps/root,simonpf/root,zzxuanyuan/root-compressor-dummy,evgeny-boger/root,BerserkerTroll/root,georgtroska/root,simonpf/root,nilqed/root,omazapa/root-old,vukasinmilosevic/root,pspe/root,CristinaCristescu/root,abhinavmoudgil95/root,agarciamontoro/root,perovic/root,evgeny-boger/root,root-mirror/root,karies/root,omazapa/root,pspe/root,gbitzes/root,mattkretz/root,bbockelm/root,Duraznos/root,simonpf/root,jrtomps/root,olifre/root,pspe/root,mattkretz/root,root-mirror/root,abhinavmoudgil95/root,sirinath/root,mattkretz/root,CristinaCristescu/root,zzxuanyuan/root,Y--/root,jrtomps/root,omazapa/root-old,BerserkerTroll/root,lgiommi/root,esakellari/root,olifre/root,esakellari/root,georgtroska/root,karies/root,gganis/root,jrtomps/root,karies/root,BerserkerTroll/root,abhinavmoudgil95/root,agarciamontoro/root,sbinet/cxx-root,gbitzes/root,0x0all/ROOT,sbinet/cxx-root,BerserkerTroll/root,mattkretz/root,mattkretz/root,mattkretz/root,arch1tect0r/root,arch1tect0r/root,esakellari/root,mattkretz/root,lgiommi/root,pspe/root,zzxuanyuan/root-compressor-dummy,beniz/root,arch1tect0r/root,sbinet/cxx-root,omazapa/root,olifre/root,Y--/root,omazapa/root-old,karies/root,jrtomps/root,gbitzes/root,zzxuanyuan/root,sirinath/root,mkret2/root,Duraznos/root,Y--/root,omazapa/root,gganis/root,omazapa/root,thomaskeck/root,lgiommi/root,lgiommi/root,beniz/root,olifre/root,jrtomps/root,davidlt/root,simonpf/root,nilqed/root,omazapa/root-old,CristinaCristescu/root,buuck/root,zzxuanyuan/root,omazapa/root,root-mirror/root,dfunke/root,veprbl/root,simonpf/root,georgtroska/root,beniz/root,CristinaCristescu/root,davidlt/root,mkret2/root,smarinac/root,Y--/root,perovic/root,pspe/root,mhuwiler/rootauto,gganis/root,mkret2/root,gbitzes/root,arch1tect0r/root,CristinaCristescu/root,nilqed/root,Duraznos/root,sawenzel/root,mkret2/root,gbitzes/root,agarciamontoro/root,nilqed/root,mhuwiler/rootauto,zzxuanyuan/root-compressor-dummy,evgeny-boger/root,root-mirror/root,sbinet/cxx-root,abhinavmoudgil95/root,lgiommi/root,davidlt/root,root-mirror/root,0x0all/ROOT