Remove useless argument

Do not pass any data to the event watcher, it is unused.

app/src/scrcpy.c

@@ -56,7 +56,7 @@ static int event_watcher(void* data, SDL_Event* event) {
 
 static void event_loop(void) {
 #ifdef CONTINUOUS_RESIZING_WORKAROUND
-    SDL_AddEventWatch(event_watcher, screen.window);
+    SDL_AddEventWatch(event_watcher, NULL);
 #endif
     SDL_Event event;
     while (SDL_WaitEvent(&event)) {