Fix for crash happening on blender exit after the bake

The issue is caused by 1a79abdad, and annoyingly it's a regression
since 2.69, so if we do 'a', this commit should be ported there.

source/blender/render/intern/source/convertblender.c

@@ -5868,7 +5868,9 @@ void RE_Database_Baking(Render *re, Main *bmain, Scene *scene, unsigned int lay,
 	re->lay= lay;
 
 	/* renderdata setup and exceptions */
-	re->r= scene->r;
+	BLI_freelistN(&re->r.layers);
+	re->r = scene->r;
+	BLI_duplicatelist(&re->r.layers, &scene->r.layers);
 	
 	RE_init_threadcount(re);