handle tables with no row labels
handle tables with no row labels

More gracefully handle the situation where the input table does
not contain a vtkStringArray column naming the rows.  Previously,
this class assumed that the first column was a vtkStringArray,
leading to a segmentation fault when it was not.

Change-Id: Ie0aeca049f23885b85a51d6c8b2a43dbc0e1afcd

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