vtkOpenGLQuadHelper now releases resources correctly if the context goes
away before the vtkOpenGLQuadHelper instance does.

Address errors on closing window in ParaView (paraview/paraview#18938).
The issues was that the OpenGL context was destoyed when the QT window
went away. vtkOpenGLQuadHelper instance held by vtkOpenGLFXAAFilter was
not cleaned up until after the context was destroyed causing errors.