patch 8.2.3848: cannot use reduce() for a string

Problem:    Cannot use reduce() for a string.
Solution:   Make reduce() work with a string. (Naruhiko Nishino, closes #9366)
diff --git a/src/errors.h b/src/errors.h
index 2ca71f1..3fd8e5a 100644
--- a/src/errors.h
+++ b/src/errors.h
@@ -843,4 +843,8 @@
 EXTERN char e_argument_of_str_must_be_list_string_dictionary_or_blob[]
 	INIT(= N_("E1250: Argument of %s must be a List, String, Dictionary or Blob"));
 EXTERN char e_list_dict_blob_or_string_required_for_argument_nr[]
-	INIT(= N_("E1228: List, Dictionary, Blob or String required for argument %d"));
+	INIT(= N_("E1251: List, Dictionary, Blob or String required for argument %d"));
+EXTERN char e_string_list_or_blob_required_for_argument_nr[]
+	INIT(= N_("E1252: String, List or Blob required for argument %d"));
+EXTERN char e_string_expected_for_argument_nr[]
+	INIT(= N_("E1253: String expected for argument %d"));