Try to fix titlebar on room dir

resources/qml/dialogs/RoomDirectory.qml

@@ -5,9 +5,10 @@
 
 import ".."
 import "../ui"
-import QtQuick 2.9
+import QtQuick 2.15
 import QtQuick.Controls 2.3
 import QtQuick.Layouts 1.3
+import QtQuick.Window 2.15
 import im.nheko 1.0
 
 ApplicationWindow {