settingssidepanel: fix re-selection in single pane mode

Gitlab: #1130
Change-Id: Icfe9efc69d69b69fbcc5c2224241f89e0b9ccca9

src/app/commoncomponents/ListSelectionView.qml

@@ -45,7 +45,7 @@ DualPaneView {
     function selectIndex(index) { viewNode.index = index }
 
     // Override this predicate if needed.
-    property bool hasValidSelection: viewNode.index >= 0
+    property bool hasValidSelection: viewNode.index >= -1
     onHasValidSelectionChanged: isSinglePaneChangedHandler()
 
     // Override BaseView.dismiss with some selection logic.

src/app/settingsview/SettingsSidePanel.qml

@@ -143,6 +143,7 @@ SidePanelBase {
     }
 
     function open(index) {
+        indexSelected(-1)
         indexSelected(index)
         root.currentIndex = index
     }