BUG: Add checks to avoid seg fault.
BUG: Add checks to avoid seg fault.

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