VTK Bug15270: Correct empty condition for vtkGlyph3DMapper
When working on an empty polydata, vtkGlyph3DMapper::GetBounds()
would
return the bounds of the glyph instead of vtkMath::UninitializedBounds.
This would be confusing because glyph's bounds has nothing to do with
the rest of the scene and discrupts
vtkRenderer::ResetCameraClippingRange. To fix this, a check condition is
added. If there is nothing inside the scene, we just return the vtkMath::UninitializedBounds.
Fixes #15270 (closed)