SDL: avoid NullPointer in SDL_GL_MakeCurrent

SDL Commits
1 
From 01b14e14e63ac85d295755880bcf7d441c4ff0ce Mon Sep 17 00:00:00 2001
From: pionere <[EMAIL REDACTED]>
Date: Tue, 12 Apr 2022 08:49:19 +0200
Subject: [PATCH] avoid NullPointer in SDL_GL_MakeCurrent

---
 src/video/SDL_video.c | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/src/video/SDL_video.c b/src/video/SDL_video.c
index 6537b4535ff..2b095243021 100644
--- a/src/video/SDL_video.c
+++ b/src/video/SDL_video.c
@@ -3924,6 +3924,10 @@ SDL_GL_MakeCurrent(SDL_Window * window, SDL_GLContext ctx)
 {
     int retval;
 
+    if (!_this) {
+        return SDL_UninitializedVideo();
+    }
+
     if (window == SDL_GL_GetCurrentWindow() &&
         ctx == SDL_GL_GetCurrentContext()) {
         /* We're already current. */