Fixed crash in GGI detection

--HG--
extra : convert_revision : svn%3Ac70aab31-4412-0410-b14c-859654838e24/trunk%4018

src/video/ggi/SDL_ggivideo.c

@@ -76,11 +76,13 @@ static int GGI_Available(void)
 {
 	ggi_visual_t *vis;
 
+	vis = NULL;
+	if (ggiInit() == 0) {
 		vis = ggiOpen(NULL);
-	if (vis != NULL) 
-	{
+		if (vis != NULL) {
 			ggiClose(vis);
 		}
+	}
 	return (vis != NULL);
 }