BUG: fix error conditions when there is no file, not to crash
BUG: fix error conditions when there is no file, not to crash

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