SDL: [KMSDRM] Fix segmentation fault

SDL Commits
1 
From c12f46b100d22a0e06a64c5b6d1baa3f446d34e6 Mon Sep 17 00:00:00 2001
From: Paul Cercueil <[EMAIL REDACTED]>
Date: Mon, 22 Mar 2021 19:03:25 +0000
Subject: [PATCH] [KMSDRM] Fix segmentation fault

Deference the windata pointer *after* checking that it's non-NULL.

Signed-off-by: Paul Cercueil <paul@crapouillou.net>
---
 src/video/kmsdrm/SDL_kmsdrmvideo.c | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/src/video/kmsdrm/SDL_kmsdrmvideo.c b/src/video/kmsdrm/SDL_kmsdrmvideo.c
index 4d1bc7ae6..48c2e8a3b 100644
--- a/src/video/kmsdrm/SDL_kmsdrmvideo.c
+++ b/src/video/kmsdrm/SDL_kmsdrmvideo.c
@@ -1071,7 +1071,7 @@ KMSDRM_DestroyWindow(_THIS, SDL_Window *window)
 {
     SDL_WindowData *windata = (SDL_WindowData *) window->driverdata;
     SDL_DisplayData *dispdata = (SDL_DisplayData *) SDL_GetDisplayForWindow(window)->driverdata;
-    SDL_VideoData *viddata = windata->viddata;
+    SDL_VideoData *viddata;
     SDL_bool is_vulkan = window->flags & SDL_WINDOW_VULKAN; /* Is this a VK window? */
     unsigned int i, j;
 
@@ -1079,6 +1079,8 @@ KMSDRM_DestroyWindow(_THIS, SDL_Window *window)
         return;
     }
 
+    viddata = windata->viddata;
+
     if ( !is_vulkan && viddata->gbm_init) {
 
         /* Destroy cursor GBM BO of the display of this window. */