Bugfix: Stratum initiate: Clear json var after freeing it, to avoid a potential double-free if retry fails before new JSON is parsed

util.c

@@ -1648,7 +1648,10 @@ bool initiate_stratum(struct pool *pool)
 	ret = true;
 out:
 	if (val)
+	{
 		json_decref(val);
+		val = NULL;
+	}
 
 	if (ret) {
 		if (!pool->stratum_url)