Severe bugfix: format->BitsPerPixel not checked in ListModes function

--HG--
extra : convert_revision : svn%3Ac70aab31-4412-0410-b14c-859654838e24/trunk%40712

src/video/xbios/SDL_xbios.c

@@ -400,9 +400,19 @@ static int XBIOS_VideoInit(_THIS, SDL_PixelFormat *vformat)
 
 static SDL_Rect **XBIOS_ListModes(_THIS, SDL_PixelFormat *format, Uint32 flags)
 {
+	unsigned int numlist;
+
 	/* 8 bits -> list 0 */
 	/* 16 bits -> list 1 */
-	return(SDL_modelist[(format->BitsPerPixel)>>4]);
+	if (format->BitsPerPixel == 15) {
+		return NULL;
+	}
+
+	numlist = (format->BitsPerPixel)>>4;
+	if (numlist>1)
+		return NULL;
+
+	return(SDL_modelist[numlist]);
 }
 
 static void XBIOS_FreeBuffers(_THIS)