Fix iteration over None
Fix iteration over None
astrofrog/glue-vispy-viewers,PennyQ/glue-3d-viewer,astrofrog/debug-windows-vispy,astrofrog/debug-windows-vispy,PennyQ/astro-vispy,glue-viz/glue-3d-viewer,astrofrog/glue-3d-viewer,glue-viz/glue-vispy-viewers