--- a/mod_rest/jsonmap.lib.lua	Sun Nov 15 16:29:48 2020 +0100
+++ b/mod_rest/jsonmap.lib.lua	Sun Nov 15 16:31:08 2020 +0100
@@ -467,7 +467,7 @@
 			type = err_typ,
 			condition = err_condition,
 			text = err_text,
-			by = error.attr.by,
+			by = error and error.attr.by or nil,
 		};
 		return t;
 	end