exception error opening gcode file if "generated by PrusaSlicer 2.3.0+win64 on" not on first line of file

[gdeconto]

Version

version 2.3.0+win64

Operating system type + version

Windows 10 build 18362.19h1_release.190318-1202

3D printer brand / version + firmware version (if known)

not important as this is an issue with prusaslicer itself
Tevo Tornado
Creality Ender 3

Behavior

"Unhandled unknown exception; terminating the application" error pops up when I try to load a gcode file that was post processed by the ArcWelder post processing filter (so that I could test G2/G3 functionality)

• Describe the problem
  PrusaSlicer appears to need to have the "generated by PrusaSlicer 2.3.0+win64 on..." line as the very first line in the gcode file

• Steps needed to reproduce the problem

1. added ArcWelder.exe (https://github.com/FormerLurker/ArcWelderLib) EXE as an output filter for PrusaSlicer in Printer Settings| Post-Processing script. This was for testing G2/G3 functionality of my printers
2. sliced the benchy.stl file as a test
3. emptied the Plater in PrusaSlicer and tried to load the resulting gcode file into PrusaSlicer Plater
4. an error popup appeared: Unhandled unknown exception; terminating the application
5. after looking at the gcode file, I tried moving the "generated by PrusaSlicer 2.3.0+win64 on ..." line to the top of the file
6. after that change, I was able to load the gcode file successfully into PrusaSlicer Plater

Is this a new feature request?
No, it is more of a fix; PrusaSlicer should be able to handle any properly formatted gcode file, including those by other slicers or post processing scripts

Project File (.3MF) where problem occurs

N/A

[bubnikv]

Will be fixed in PrusaSlicer 2.4.0-alpha1.