[server] Make Display::dispatchEvents also work when event loop is started

Just delegates to dispatch in the d-ptr if the Display is already running.

src/wayland/display.cpp

@@ -150,10 +150,13 @@ void Display::startLoop()
 
 void Display::dispatchEvents(int msecTimeout)
 {
-    Q_ASSERT(!d->running);
     Q_ASSERT(d->display);
-    wl_event_loop_dispatch(d->loop, msecTimeout);
-    wl_display_flush_clients(d->display);
+    if (d->running) {
+        d->dispatch();
+    } else {
+        wl_event_loop_dispatch(d->loop, msecTimeout);
+        wl_display_flush_clients(d->display);
+    }
 }
 
 void Display::terminate()

src/wayland/display.h

@@ -81,7 +81,8 @@ public:
     /**
      * Dispatches pending events in a blocking way. May only be used if the Display is
      * created and started before the QCoreApplication is created. Once the QCoreApplication
-     * is created and the event loop is started this method may no longer be invoked.
+     * is created and the event loop is started this method delegates to the normal dispatch
+     * handling.
      * @see startLoop
      **/
     void dispatchEvents(int msecTimeout = -1);