SDL: Don't save temporary mode changes to the desktop mode

SDL Commits
1 
From 24ec2ed785f9ca5315a059ecfefd8f9531405958 Mon Sep 17 00:00:00 2001
From: Sam Lantinga <[EMAIL REDACTED]>
Date: Sun, 2 Mar 2025 10:55:26 -0800
Subject: [PATCH] Don't save temporary mode changes to the desktop mode

Fixes https://github.com/libsdl-org/SDL/issues/12441
---
 src/video/SDL_video.c | 5 +++++
 1 file changed, 5 insertions(+)

diff --git a/src/video/SDL_video.c b/src/video/SDL_video.c
index 3a400d8131b20..8b67558f5fa0e 100644
--- a/src/video/SDL_video.c
+++ b/src/video/SDL_video.c
@@ -1435,6 +1435,11 @@ void SDL_SetDesktopDisplayMode(SDL_VideoDisplay *display, const SDL_DisplayMode
 {
     SDL_DisplayMode last_mode;
 
+    if (display->fullscreen_window) {
+        // This is a temporary mode change, don't save the desktop mode
+        return;
+    }
+
     SDL_copyp(&last_mode, &display->desktop_mode);
 
     if (display->desktop_mode.internal) {