BUG: fixed null dereference found by clang static analyzer
BUG: fixed null dereference found by clang static analyzer

Change-Id: I1a22d3592621df6f992cddfef2440f14b3643abc

gram526/VTK,sankhesh/VTK,aashish24/VTK-old,aashish24/VTK-old,ashray/VTK-EVM,gram526/VTK,collects/VTK,ashray/VTK-EVM,hendradarwin/VTK,johnkit/vtk-dev,msmolens/VTK,msmolens/VTK,collects/VTK,sankhesh/VTK,candy7393/VTK,mspark93/VTK,sumedhasingla/VTK,jmerkow/VTK,sumedhasingla/VTK,collects/VTK,ashray/VTK-EVM,demarle/VTK,aashish24/VTK-old,mspark93/VTK,demarle/VTK,biddisco/VTK,jmerkow/VTK,msmolens/VTK,sankhesh/VTK,berendkleinhaneveld/VTK,SimVascular/VTK,demarle/VTK,demarle/VTK,ashray/VTK-EVM,mspark93/VTK,berendkleinhaneveld/VTK,sumedhasingla/VTK,SimVascular/VTK,johnkit/vtk-dev,sumedhasingla/VTK,SimVascular/VTK,msmolens/VTK,msmolens/VTK,johnkit/vtk-dev,johnkit/vtk-dev,berendkleinhaneveld/VTK,ashray/VTK-EVM,keithroe/vtkoptix,sankhesh/VTK,mspark93/VTK,msmolens/VTK,keithroe/vtkoptix,jmerkow/VTK,ashray/VTK-EVM,hendradarwin/VTK,candy7393/VTK,sankhesh/VTK,keithroe/vtkoptix,candy7393/VTK,biddisco/VTK,mspark93/VTK,jmerkow/VTK,sankhesh/VTK,biddisco/VTK,hendradarwin/VTK,johnkit/vtk-dev,gram526/VTK,mspark93/VTK,keithroe/vtkoptix,mspark93/VTK,msmolens/VTK,gram526/VTK,sankhesh/VTK,jmerkow/VTK,biddisco/VTK,keithroe/vtkoptix,aashish24/VTK-old,keithroe/vtkoptix,gram526/VTK,msmolens/VTK,mspark93/VTK,johnkit/vtk-dev,hendradarwin/VTK,hendradarwin/VTK,gram526/VTK,ashray/VTK-EVM,demarle/VTK,candy7393/VTK,berendkleinhaneveld/VTK,demarle/VTK,SimVascular/VTK,keithroe/vtkoptix,candy7393/VTK,sumedhasingla/VTK,jmerkow/VTK,biddisco/VTK,sumedhasingla/VTK,collects/VTK,collects/VTK,candy7393/VTK,berendkleinhaneveld/VTK,SimVascular/VTK,gram526/VTK,berendkleinhaneveld/VTK,SimVascular/VTK,sumedhasingla/VTK,candy7393/VTK,candy7393/VTK,hendradarwin/VTK,hendradarwin/VTK,biddisco/VTK,demarle/VTK,gram526/VTK,biddisco/VTK,johnkit/vtk-dev,aashish24/VTK-old,jmerkow/VTK,SimVascular/VTK,sumedhasingla/VTK,collects/VTK,berendkleinhaneveld/VTK,keithroe/vtkoptix,jmerkow/VTK,sankhesh/VTK,aashish24/VTK-old,demarle/VTK,ashray/VTK-EVM,SimVascular/VTK