Error message: "Flow::mm3_per_mm() produced negative flow."  

Error message: "Flow::mm3_per_mm() produced negative flow."

I'm experimenting with OpenSCAD and platonic solids. I opened the generated STL with Prusa-Slicer (Version 2.3.0+linux-x64) just to verify results. Using standard settings (0.15mm QUALITY, Prusament PLA, Prusa i3 MK3S) on "Slice now" I get an error "There is an object with no extrusion on the first layer", which is correct, because all objects are hovering above the surface. So I set supports to "Supports on build plate only" and try "Slice now" again.

Now I get a big error message "PrusaSlicer has encountered an error", "Flow::mm3_per_mm() produced negative flow. Did you set some extrusion width to small?"

No, I didn't. At least not to my knowledge. I would share my STL, but the forum would not let me.
If I can support you in providing more details, please let me know.

The fault is not critical for me, because I just wanted to have a look and not really slice and print the items, but I'd like to know, what happens.