qml/MainDisplay: Fix keyboard focus loss when clearing the 'localMenuDelegate'

The previous implementation made us lose the keyboard focus each time we set 'localMenuDelegate' to null.

modules/gui/qt/maininterface/qml/BannerSources.qml

@@ -340,6 +340,7 @@ FocusScope {
                         onVisibleChanged: {
                             //reset the focus on the global group when the local group is hidden,
                             //this avoids losing the focus if the subview changes
+                            // FIXME: This block needs refactor for keyboard focus.
                             if (!visible && localMenuGroup.focus) {
                                 localMenuGroup.focus = false
                                 globalMenuGroup.focus = true

modules/gui/qt/maininterface/qml/MainDisplay.qml

@@ -197,7 +197,6 @@ FocusScope {
                     model: root.tabModel
 
                     onItemClicked: {
-                        sourcesBanner.localMenuDelegate = null
                         var name = root.tabModel.get(index).name
                         selectedIndex = index
                         history.push(["mc", name])