Handle more exceptional conditions.
Handle more exceptional conditions.

Don't accept requests for unique values of components which do not exist.
Do rebuild list of unique values when key has been modified but does not
yet include a list of unique values.

Change-Id: Iee549d68aa442fe63ce6a1f3e5c865bf03ebb345

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