better handling of null objects
better handling of null objects

sumedhasingla/VTK,keithroe/vtkoptix,spthaolt/VTK,msmolens/VTK,ashray/VTK-EVM,gram526/VTK,gram526/VTK,naucoin/VTKSlicerWidgets,naucoin/VTKSlicerWidgets,jmerkow/VTK,ashray/VTK-EVM,Wuteyan/VTK,jeffbaumes/jeffbaumes-vtk,sgh/vtk,ashray/VTK-EVM,cjh1/VTK,biddisco/VTK,sgh/vtk,jeffbaumes/jeffbaumes-vtk,sgh/vtk,msmolens/VTK,gram526/VTK,berendkleinhaneveld/VTK,biddisco/VTK,gram526/VTK,johnkit/vtk-dev,aashish24/VTK-old,ashray/VTK-EVM,sgh/vtk,sankhesh/VTK,collects/VTK,mspark93/VTK,biddisco/VTK,daviddoria/PointGraphsPhase1,mspark93/VTK,sgh/vtk,collects/VTK,candy7393/VTK,jmerkow/VTK,gram526/VTK,arnaudgelas/VTK,sumedhasingla/VTK,candy7393/VTK,candy7393/VTK,demarle/VTK,gram526/VTK,johnkit/vtk-dev,candy7393/VTK,gram526/VTK,jmerkow/VTK,sumedhasingla/VTK,berendkleinhaneveld/VTK,johnkit/vtk-dev,demarle/VTK,Wuteyan/VTK,daviddoria/PointGraphsPhase1,jeffbaumes/jeffbaumes-vtk,jmerkow/VTK,jmerkow/VTK,daviddoria/PointGraphsPhase1,berendkleinhaneveld/VTK,sankhesh/VTK,sankhesh/VTK,candy7393/VTK,sankhesh/VTK,spthaolt/VTK,SimVascular/VTK,spthaolt/VTK,berendkleinhaneveld/VTK,naucoin/VTKSlicerWidgets,gram526/VTK,demarle/VTK,candy7393/VTK,johnkit/vtk-dev,arnaudgelas/VTK,demarle/VTK,SimVascular/VTK,SimVascular/VTK,sumedhasingla/VTK,jmerkow/VTK,Wuteyan/VTK,sgh/vtk,candy7393/VTK,berendkleinhaneveld/VTK,hendradarwin/VTK,jmerkow/VTK,berendkleinhaneveld/VTK,johnkit/vtk-dev,jeffbaumes/jeffbaumes-vtk,mspark93/VTK,SimVascular/VTK,SimVascular/VTK,mspark93/VTK,demarle/VTK,collects/VTK,biddisco/VTK,cjh1/VTK,keithroe/vtkoptix,jeffbaumes/jeffbaumes-vtk,sankhesh/VTK,hendradarwin/VTK,naucoin/VTKSlicerWidgets,hendradarwin/VTK,aashish24/VTK-old,mspark93/VTK,demarle/VTK,biddisco/VTK,demarle/VTK,keithroe/vtkoptix,sankhesh/VTK,msmolens/VTK,sumedhasingla/VTK,aashish24/VTK-old,mspark93/VTK,daviddoria/PointGraphsPhase1,msmolens/VTK,SimVascular/VTK,keithroe/vtkoptix,arnaudgelas/VTK,keithroe/vtkoptix,collects/VTK,hendradarwin/VTK,daviddoria/PointGraphsPhase1,keithroe/vtkoptix,jeffbaumes/jeffbaumes-vtk,sumedhasingla/VTK,spthaolt/VTK,aashish24/VTK-old,cjh1/VTK,msmolens/VTK,sankhesh/VTK,Wuteyan/VTK,sumedhasingla/VTK,spthaolt/VTK,collects/VTK,mspark93/VTK,spthaolt/VTK,arnaudgelas/VTK,msmolens/VTK,jmerkow/VTK,johnkit/vtk-dev,naucoin/VTKSlicerWidgets,sumedhasingla/VTK,arnaudgelas/VTK,aashish24/VTK-old,msmolens/VTK,sankhesh/VTK,ashray/VTK-EVM,cjh1/VTK,keithroe/vtkoptix,hendradarwin/VTK,Wuteyan/VTK,cjh1/VTK,biddisco/VTK,daviddoria/PointGraphsPhase1,Wuteyan/VTK,berendkleinhaneveld/VTK,arnaudgelas/VTK,candy7393/VTK,aashish24/VTK-old,cjh1/VTK,collects/VTK,hendradarwin/VTK,demarle/VTK,msmolens/VTK,keithroe/vtkoptix,johnkit/vtk-dev,biddisco/VTK,ashray/VTK-EVM,mspark93/VTK,SimVascular/VTK,ashray/VTK-EVM,spthaolt/VTK,naucoin/VTKSlicerWidgets,SimVascular/VTK,Wuteyan/VTK,ashray/VTK-EVM,hendradarwin/VTK