[LinuxCNC/linuxcnc Issue#311] linuxcnc reports “Unable to open file <>” on any gcode error

Here are the steps I follow to reproduce the issue:

open sim/axis
load gcode file with error

This is what I expected to happen:

get a detailed report of the error

This is what happened instead:

Unable to open file <>

It worked properly before this:

still present in 2.7.10, not in 2.7.9
https://github.com/LinuxCNC/linuxcnc/compare/v2.7.9…v2.7.10

Information about my hardware and software:

A binary I built myself v2.8.0-pre1-3277-g063b79b3d