SDL: SDL_x11modes: fix -Wunused-variable

SDL Commits
1 
From eb8eb621b1bbde49be4fc7b5bef7942adf052746 Mon Sep 17 00:00:00 2001
From: Anonymous Maarten <[EMAIL REDACTED]>
Date: Thu, 6 Oct 2022 22:49:17 +0200
Subject: [PATCH] SDL_x11modes: fix -Wunused-variable

---
 src/video/x11/SDL_x11modes.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/src/video/x11/SDL_x11modes.c b/src/video/x11/SDL_x11modes.c
index 8e38847158b0..da63afdcbf8b 100644
--- a/src/video/x11/SDL_x11modes.c
+++ b/src/video/x11/SDL_x11modes.c
@@ -833,6 +833,8 @@ X11_SetDisplayMode(_THIS, SDL_VideoDisplay * sdl_display, SDL_DisplayMode * mode
             return SDL_SetError("X11_XRRSetCrtcConfig failed");
         }
     }
+#else
+    (void)data;
 #endif /* SDL_VIDEO_DRIVER_X11_XRANDR */
 
     return 0;