SDL: wayland: Only dispatch on fullscreen set when the window is visible.

SDL Commits
1 
From 7082fb04af66367cd23f2fe083034db587612c46 Mon Sep 17 00:00:00 2001
From: Ethan Lee <[EMAIL REDACTED]>
Date: Mon, 2 Aug 2021 22:42:28 -0400
Subject: [PATCH] wayland: Only dispatch on fullscreen set when the window is
 visible.

Fixes hang-on-startup described in #4572.
---
 src/video/wayland/SDL_waylandwindow.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/src/video/wayland/SDL_waylandwindow.c b/src/video/wayland/SDL_waylandwindow.c
index 49db037a8..29823e2ec 100644
--- a/src/video/wayland/SDL_waylandwindow.c
+++ b/src/video/wayland/SDL_waylandwindow.c
@@ -962,7 +962,7 @@ Wayland_SetWindowFullscreen(_THIS, SDL_Window * window,
      *
      * -flibit
      */
-    if (viddata->shell.libdecor) {
+    if (viddata->shell.libdecor && (window->flags & SDL_WINDOW_SHOWN)) {
         WAYLAND_wl_display_dispatch(viddata->display);
     }
 #endif