Fix double to unsigned char cast error on clang compiler.
Fix double to unsigned char cast error on clang compiler.

Change-Id: I3979f3eeb2407a9924e57cf4b8540ea67693807e

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