fix memory leak in vtkImageDataLIC2D
fix memory leak in vtkImageDataLIC2D

    * delete MagShader in destructor and if shader build was not successful
    * don't try to use the MagShader if we haven't build it

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