fix(FoldableHeader): do not display the switch if the model is empty

makes no sense to be able to arrange by community/collection if the the
underlying model is empty

ui/imports/shared/controls/FoldableHeader.qml

@@ -55,7 +55,7 @@ Rectangle {
             id: modeSwitch
             objectName: "switch"
 
-            visible: !!text
+            visible: !!text && !!root.ListView.view && root.ListView.view.model && root.ListView.view.model.count
             LayoutMirroring.enabled: true
             LayoutMirroring.childrenInherit: true
             textColor: Theme.palette.baseColor1