Fix gamepad menu focus and dismissal issues

app/gui/NavigableMenuItem.qml

@@ -2,6 +2,10 @@ import QtQuick 2.0
 import QtQuick.Controls 2.2
 
 MenuItem {
+    // Qt 5.10 has a menu property, but we need to support 5.9
+    // so we must make our own.
+    property Menu parentMenu
+
     // Ensure focus can't be given to an invisible item
     enabled: visible
     height: visible ? implicitHeight : 0
@@ -10,4 +14,8 @@ MenuItem {
     Keys.onReturnPressed: {
         triggered()
     }
+
+    Keys.onEscapePressed: {
+        parentMenu.close()
+    }
 }