Keep the notification centre below the bar

shell/plugins/notification-center/NotificationCenter.qml

@@ -20,6 +20,12 @@ Item {
   property bool doNotDisturb: false
   readonly property bool empty: root.entries.length === 0
 
+  readonly property int barInset: {
+    var bar = root.shell ? root.shell.bar : null
+    if (!bar || bar.barHidden === true) return 0
+    return Math.max(0, bar.barSize || 0)
+  }
+
   function open(payloadJson) {
     root.opened = true
     root.refresh()
@@ -114,7 +120,7 @@ Item {
     Card {
       anchors.top: parent.top
       anchors.right: parent.right
-      anchors.topMargin: Style.spaceReal(10)
+      anchors.topMargin: Style.spaceReal(10) + root.barInset
       anchors.rightMargin: Style.spaceReal(10)
       implicitWidth: Style.spaceReal(440)
       implicitHeight: Style.spaceReal(420)