sidebar: Fix text color not updating on theme change
Inside the ListView of the sidebar the topmost delegate, which currently is the "Appearance" category, does not update it's text color when a theme change happens resulting in almost unreadable text.
Unforunately I could not figure out why the textcolor property of the very first delegate does not update when changing the theme(broken property binding?) but explicitly setting the colorSet iniside the ListView alleviates this issue.
It's noteworthy to point out that when the delegate gets destroyed by scrolling it out of view when it's re-created it behaves properly on theme changes.