Fix automatic refresh of the panel widget
Created by: mariospr
This widget installs a GSourceFunc to be triggered on a 60 seconds timeout but it does not explicitly return GLib.SOURCE_CONTINUE in the callback, meaning that the source will be removed after it gets called once, leaving the label outdated forever.
This fixes this problem by explicitly returning GLib.SOURCE_CONTINUE there.
https://github.com/projecthamster/hamster-shell-extension/issues/189