mf: Fix a typo when setting event attribute.

dlls/mf/session.c

@@ -1189,7 +1189,7 @@ static HRESULT session_set_current_topology(struct media_session *session, IMFTo
     {
         IMFMediaEvent_SetUINT64(event, &MF_EVENT_START_PRESENTATION_TIME, 0);
         IMFMediaEvent_SetUINT64(event, &MF_EVENT_PRESENTATION_TIME_OFFSET, 0);
-        IMFMediaEvent_GetUINT64(event, &MF_EVENT_START_PRESENTATION_TIME_AT_OUTPUT, 0);
+        IMFMediaEvent_SetUINT64(event, &MF_EVENT_START_PRESENTATION_TIME_AT_OUTPUT, 0);
 
         IMFMediaEventQueue_QueueEvent(session->event_queue, event);
         IMFMediaEvent_Release(event);