BUG: Fixes bug #10686, zero min/max problem.
BUG: Fixes bug #10686, zero min/max problem.

Handle the case where min and max are both zero. Also took the
opportunity to fix the code up a little for min/max variables.

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