FIX Jira issue #ROOT-8715 Bad interaction of TTreeViewer vs cling
FIX Jira issue #ROOT-8715 Bad interaction of TTreeViewer vs cling

Prevent the following error messages about redefinition of global variables when starting a TTreeViewer a second time:

root [0] new TTreeViewer
(TTreeViewer *) 0x2c77630
(TTreeViewer *) 0x2c77630
root [1] new TTreeViewer
input_line_44:2:15: error: redefinition of 'gTV'
 TTreeViewer *gTV = (TTreeViewer*)0x4027000
              ^
input_line_31:2:15: note: previous definition is here
 TTreeViewer *gTV = (TTreeViewer*)0x2c77630
              ^
input_line_45:2:9: error: redefinition of 'tv__tree'
 TTree *tv__tree = 0;
        ^
input_line_35:2:9: note: previous definition is here
 TTree *tv__tree = 0;
        ^
input_line_46:2:9: error: redefinition of 'tv__tree_list'
 TList *tv__tree_list = new TList;
        ^
input_line_36:2:9: note: previous definition is here
 TList *tv__tree_list = new TList;
        ^
input_line_47:2:9: error: redefinition of 'tv__tree_file'
 TFile *tv__tree_file = 0;
        ^
input_line_37:2:9: note: previous definition is here
 TFile *tv__tree_file = 0;
        ^
(TTreeViewer *) 0x4027000

davidlt/root,buuck/root,zzxuanyuan/root,abhinavmoudgil95/root,satyarth934/root,BerserkerTroll/root,mhuwiler/rootauto,beniz/root,olifre/root,bbockelm/root,satyarth934/root,simonpf/root,beniz/root,olifre/root,buuck/root,olifre/root,BerserkerTroll/root,simonpf/root,olifre/root,agarciamontoro/root,beniz/root,mhuwiler/rootauto,olifre/root,karies/root,zzxuanyuan/root,mhuwiler/rootauto,BerserkerTroll/root,BerserkerTroll/root,karies/root,root-mirror/root,bbockelm/root,zzxuanyuan/root,mhuwiler/rootauto,davidlt/root,abhinavmoudgil95/root,zzxuanyuan/root-compressor-dummy,mhuwiler/rootauto,karies/root,BerserkerTroll/root,zzxuanyuan/root,zzxuanyuan/root,mhuwiler/rootauto,simonpf/root,root-mirror/root,agarciamontoro/root,BerserkerTroll/root,simonpf/root,root-mirror/root,abhinavmoudgil95/root,buuck/root,zzxuanyuan/root-compressor-dummy,agarciamontoro/root,BerserkerTroll/root,zzxuanyuan/root,agarciamontoro/root,olifre/root,bbockelm/root,buuck/root,bbockelm/root,root-mirror/root,satyarth934/root,zzxuanyuan/root,buuck/root,abhinavmoudgil95/root,bbockelm/root,buuck/root,beniz/root,zzxuanyuan/root,olifre/root,mhuwiler/rootauto,bbockelm/root,zzxuanyuan/root-compressor-dummy,root-mirror/root,buuck/root,satyarth934/root,satyarth934/root,abhinavmoudgil95/root,bbockelm/root,buuck/root,satyarth934/root,root-mirror/root,agarciamontoro/root,zzxuanyuan/root-compressor-dummy,agarciamontoro/root,simonpf/root,olifre/root,agarciamontoro/root,simonpf/root,beniz/root,root-mirror/root,karies/root,zzxuanyuan/root,zzxuanyuan/root-compressor-dummy,satyarth934/root,karies/root,agarciamontoro/root,karies/root,agarciamontoro/root,buuck/root,karies/root,simonpf/root,davidlt/root,zzxuanyuan/root-compressor-dummy,zzxuanyuan/root-compressor-dummy,root-mirror/root,buuck/root,zzxuanyuan/root-compressor-dummy,davidlt/root,satyarth934/root,mhuwiler/rootauto,bbockelm/root,mhuwiler/rootauto,beniz/root,beniz/root,olifre/root,abhinavmoudgil95/root,satyarth934/root,zzxuanyuan/root,BerserkerTroll/root,simonpf/root,zzxuanyuan/root-compressor-dummy,abhinavmoudgil95/root,bbockelm/root,karies/root,zzxuanyuan/root-compressor-dummy,olifre/root,bbockelm/root,simonpf/root,davidlt/root,abhinavmoudgil95/root,zzxuanyuan/root-compressor-dummy,beniz/root,abhinavmoudgil95/root,abhinavmoudgil95/root,simonpf/root,beniz/root,davidlt/root,karies/root,root-mirror/root,BerserkerTroll/root,root-mirror/root,beniz/root,bbockelm/root,karies/root,BerserkerTroll/root,davidlt/root,agarciamontoro/root,davidlt/root,satyarth934/root,simonpf/root,satyarth934/root,root-mirror/root,beniz/root,mhuwiler/rootauto,agarciamontoro/root,olifre/root,karies/root,zzxuanyuan/root,buuck/root,BerserkerTroll/root,davidlt/root,mhuwiler/rootauto,abhinavmoudgil95/root,davidlt/root,davidlt/root,zzxuanyuan/root