Thanks for your question. Zero width traces are permitted in Gerber and considered zero area (i.e used 'for reference only'). Since they are considered zero width (or invisible) they will not appear on the final artwork released to PCB production and be ignored by the FAB 3000 DFM Checker.
However if you want FAB 3000 to detect these zero width traces, change the Aperture Dcode referenced from 0 to 0.1 mil (or something small) - it will then immediately be flagged by minimum trace. Here's how:
Now ALL those 0-width paths that referenced the Aperture you edited, will have the new width you assigned.
Here's a tutorial movie (no sound showing these steps).