Fix GlobalMenu initialization on other platforms

Cherry-pick of 76919a13b8

src/qml/GlobalMenuStub.qml

@@ -0,0 +1,10 @@
+// SPDX-FileCopyrightText: 2025 Joshua Goins <josh@redstrate.com
+// SPDX-License-Identifier: GPL-3.0-or-later
+
+import QtQuick
+
+import org.kde.neochat
+
+Item {
+    required property NeoChatConnection connection
+}