LDAP attribute mapping for ldap_user_attr_picture doesn't'work with Active Directory

When I set ldap_user_attr_picture=thumbnailPhoto (or jpegPhoto, doesn't matter), it causes internal server error during user auth by ldap query with the following log message:

ERROR 04-15 15:56:48.460 o.a.d.a.l.m.e.DefaultAttribute:523 [pr-8080-exec-12] - ERR_13215_VALUE_EXPECT_STRING The value is expected to be a String
ERROR 04-15 15:56:48.461 o.a.o.c.l.LdapLoginManager:231 [pr-8080-exec-12] - Unexpected exception.
org.apache.directory.api.ldap.model.exception.LdapInvalidAttributeValueException: ERR_13215_VALUE_EXPECT_STRING The value is expected to be a String
at org.apache.directory.api.ldap.model.entry.DefaultAttribute.getString(DefaultAttribute.java:524)
at org.apache.openmeetings.core.ldap.LdapLoginManager.getStringAttr(LdapLoginManager.java:153)
at org.apache.openmeetings.core.ldap.LdapLoginManager$LdapWorker.getUser(LdapLoginManager.java:371)
at org.apache.openmeetings.core.ldap.LdapLoginManager.login(LdapLoginManager.java:215)   

Seems like there is STRING value expected but Active Directory contains:

thumbnailPhoto: <ldp: Binary blob 68590 bytes>;

jpegPhoto: <ldp: Binary blob 68590 bytes>;