on macOS:
While running game code:
File "renpy/common/00start.rpy", line 210, in script call
call _gl_test
File "renpy/common/00gltest.rpy", line 390, in script
$ __gl_test()
File "renpy/common/00start.rpy", line 210, in script call
call _gl_test
File "renpy/common/00gltest.rpy", line 390, in script
$ __gl_test()
File "renpy/common/00gltest.rpy", line 390, in <module>
$ __gl_test()
File "renpy/common/00gltest.rpy", line 317, in _m1_00gltest__gl_test
_gl_performance_test()
File "renpy/common/00gltest.rpy", line 342, in _gl_performance_test
ui.interact(suppress_underlay=True, suppress_overlay=True)
OSError: Couldn't find file 'gui/window_icon.png'.
EDIT: Nevermind, was caused by the Walkthrough Mod.