[wayland] Abort if Xwayland connection breaks

If Xwayland goes down it's better to abort than staying alive. If
Xwayland goes down the next roundtrip to X (most likely during call
to xStackingOrder) will just freeze completely, which is kind of the
worst as one cannot VT-switch anymore. So a clean abort is a bad but
better solution.

wayland_server.cpp

@@ -102,6 +102,11 @@ int WaylandServer::createXWaylandConnection()
         return -1;
     }
     m_xwaylandConnection = m_display->createClient(sx[0]);
+    connect(m_xwaylandConnection, &KWayland::Server::ClientConnection::disconnected, this,
+        [] {
+            qFatal("Xwayland Connection died");
+        }
+    );
     return sx[1];
 }