Check if there is a `keyImages` attribute before accessing it, and return
an empty list in case it isn't available. Fixes a recent crash with
`Prison Architect - eureka Update 1` DLC.
Exit early from `download_image` if the requested image is currently being
downloaded. This avoids multiple preparations and loading callbacks for
queued images.
Remove checking for supported OS when creating the icon. Now we create
icons in `icns` format for `Darwin` irregardless the fact we don't use them
for anything.
1f06c87743