The tray icon was loaded from desktop/build/icon.png, but build/ is
electron-builder's default buildResources directory, whose contents are
not packaged into the app. The icon therefore existed when running from
source but was missing in every released build, leaving an empty tray
icon.
Load the icon from the packaged app root instead and add icon.png there,
rendered from the circular logo.svg so it has transparent corners rather
than the square full-bleed source artwork.
Fixes#2668
kolaente