Fix issue if there aren't any blocks.
Fix issue if there aren't any blocks.

mspark93/VTK,mspark93/VTK,demarle/VTK,candy7393/VTK,keithroe/vtkoptix,keithroe/vtkoptix,SimVascular/VTK,demarle/VTK,keithroe/vtkoptix,sumedhasingla/VTK,sumedhasingla/VTK,candy7393/VTK,SimVascular/VTK,gram526/VTK,sankhesh/VTK,demarle/VTK,msmolens/VTK,candy7393/VTK,gram526/VTK,msmolens/VTK,demarle/VTK,demarle/VTK,msmolens/VTK,SimVascular/VTK,sankhesh/VTK,SimVascular/VTK,sumedhasingla/VTK,msmolens/VTK,SimVascular/VTK,sankhesh/VTK,sankhesh/VTK,sankhesh/VTK,sankhesh/VTK,SimVascular/VTK,mspark93/VTK,jmerkow/VTK,keithroe/vtkoptix,keithroe/vtkoptix,msmolens/VTK,candy7393/VTK,sumedhasingla/VTK,mspark93/VTK,jmerkow/VTK,gram526/VTK,sumedhasingla/VTK,keithroe/vtkoptix,gram526/VTK,candy7393/VTK,gram526/VTK,keithroe/vtkoptix,msmolens/VTK,mspark93/VTK,sumedhasingla/VTK,jmerkow/VTK,candy7393/VTK,gram526/VTK,candy7393/VTK,gram526/VTK,sumedhasingla/VTK,demarle/VTK,demarle/VTK,SimVascular/VTK,msmolens/VTK,mspark93/VTK,msmolens/VTK,sumedhasingla/VTK,jmerkow/VTK,sankhesh/VTK,jmerkow/VTK,gram526/VTK,demarle/VTK,jmerkow/VTK,candy7393/VTK,sankhesh/VTK,SimVascular/VTK,mspark93/VTK,jmerkow/VTK,keithroe/vtkoptix,jmerkow/VTK,mspark93/VTK