Fix panel array guards

The `Bar` uses a `Repeater` when building out the models. This has the
effect of marshalling the configuration, and causing JSON arrays to
become sequence wrappers.

A couple of the plugins had been checking for the existence of array
values with `Array.isArray`, which fails for the sequence wrappers,
causing the values to be ignored. This breaks associated functionality
(the "hide" and "pin" actions in the systray had stopped working, as had
exit node selection in Tailscale).

Switching the guards to use `instanceof Array` works correctly for
sequence values (as well as arrays).

shell/plugins/bar/widgets/Tray.qml

@@ -18,8 +18,8 @@ BarWidget {
   property var activeTrayAnchor: null
   readonly property color foreground: bar ? bar.foreground : Color.foreground
   readonly property string fontFamily: bar ? bar.fontFamily : Style.font.family
-  readonly property var pinnedIds: Array.isArray(settings.pinned) ? settings.pinned : []
-  readonly property var hiddenIds: Array.isArray(settings.hidden) ? settings.hidden : []
+  readonly property var pinnedIds: settings.pinned instanceof Array ? settings.pinned : []
+  readonly property var hiddenIds: settings.hidden instanceof Array ? settings.hidden : []
   readonly property var pinnedItems: bucket("pinned")
   readonly property var drawerItems: bucket("drawer")
   readonly property var allItems: bucket("all")