wayland_server: create a new screen locker connection when the greeter gets restarted

Otherwise, Wayland objects and protocol errors can cause the new instance to not start

src/wayland_server.cpp

@@ -625,16 +625,6 @@ void WaylandServer::initScreenLocker()
     ScreenLocker::KSldApp::self()->setGreeterEnvironment(kwinApp()->processStartupEnvironment());
 
     connect(ScreenLocker::KSldApp::self(), &ScreenLocker::KSldApp::aboutToLock, this, [this, screenLockerApp]() {
-        if (m_screenLockerClientConnection) {
-            // Already sent data to KScreenLocker.
-            return;
-        }
-        int clientFd = createScreenLockerConnection();
-        if (clientFd < 0) {
-            return;
-        }
-        ScreenLocker::KSldApp::self()->setWaylandFd(clientFd);
-
         new LockScreenPresentationWatcher(this);
 
         const QList<SeatInterface *> seatIfaces = m_display->seats();
@@ -644,6 +634,19 @@ void WaylandServer::initScreenLocker()
         }
     });
 
+    connect(ScreenLocker::KSldApp::self(), &ScreenLocker::KSldApp::aboutToStartGreeter, this, [this]() {
+        if (m_screenLockerClientConnection) {
+            m_screenLockerClientConnection->destroy();
+            delete m_screenLockerClientConnection;
+            m_screenLockerClientConnection = nullptr;
+        }
+        int clientFd = createScreenLockerConnection();
+        if (clientFd < 0) {
+            return;
+        }
+        ScreenLocker::KSldApp::self()->setWaylandFd(clientFd);
+    });
+
     connect(ScreenLocker::KSldApp::self(), &ScreenLocker::KSldApp::unlocked, this, [this, screenLockerApp]() {
         if (m_screenLockerClientConnection) {
             m_screenLockerClientConnection->destroy();