Check for tab container existence, see ROOT-6253.
Check for tab container existence, see ROOT-6253.

(cherry picked from v5-34-00-patches commit 05790b6f1f099c1aa43f5146d4c08bff2612adf0)

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