appimage-builder crashes when no icon is present

[benklop]

I am packaging a command line ruby app, and I have no need for n icon (or indeed a .desktop file). I would like to avoid including unnecessary files like an icon inside, but I get the following error:

INFO:main:Running desktop entry setup
INFO:root:Looking app icon at: /work/AppDir/usr/share/icons
INFO:root:Looking app icon at: /work/AppDir/usr/share/pixmaps
INFO:root:Looking app icon at: /work/AppDir/usr/local/share/icons
INFO:root:Looking app icon at: /work/AppDir/usr/local/share/pixmaps
INFO:root:Looking app icon at: /icons
INFO:root:Looking app icon at: /pixmaps
Traceback (most recent call last):
  File "/usr/lib64/python3.8/runpy.py", line 194, in _run_module_as_main
    return _run_code(code, main_globals, None,
  File "/usr/lib64/python3.8/runpy.py", line 87, in _run_code
    exec(code, run_globals)
  File "/work/appimage-builder/appimagebuilder/__main__.py", line 63, in <module>
    __main__()
  File "/work/appimage-builder/appimagebuilder/__main__.py", line 50, in __main__
    invoker.execute(commands)
  File "/work/appimage-builder/appimagebuilder/invoker.py", line 29, in execute
    command()
  File "/work/appimage-builder/appimagebuilder/commands/setup_app_info.py", line 29, in __call__
    icon_bundler.bundle_icon()
  File "/work/appimage-builder/appimagebuilder/modules/setup/icon_bundler.py", line 35, in bundle_icon
    raise IconBundler.Error("Unable to find any app icon named: %s" % self.icon)
appimagebuilder.modules.setup.icon_bundler.Error: Unable to find any app icon named: application-vnd.appimage

When I was using the AppImage release to package (instead of installing appimage-builder with pip or git), it picks up its own icon temporarily extracted and uses that.