There's a "no-item" item in the base game now. It's being used when filtering a splitter via circuit but not supplying any signal (probably introduced with the respective update). Being a gray crossed circle, I find it much more aesthetic and clear than the destruction planner.
So just suggesting to use this for the mod :)

Was that mentioned in the patch notes? Very sneaky!

I suppose this makes those "null item" mods obsolete (unless they want to do fluids etc.).

Now that I mention it, I think I do remember some debate about the "no-item" icon being less visible than the deconstruction planner, and therefore less preferable. However I disagree.

Implemented in 0.1.1.