(ITS#4823) Cannot use zero-length IA5 String

Full_Name: Kazu Nisumura
Version: 2.3.33
OS: Linux
URL: ftp://ftp.openldap.org/incoming/
Submission from: (NULL) (211.120.78.45)


When I was trying to add an entry like this using
ldapadd(1):

dn: cn=name,dc=example,dc=com
objectClass: inetOrgPerson
cn: name
sn: name
mail: 

slapd returned invalidAttributeSyntax(21) error on the mail
(IA5 String)
attribute.
According to RFC4517, zero-length IA5 String should be
allowed.