On all these columns:
phpbb_users.user_newpasswd
phpbb_users.user_password

and

phpbb_forums.forum_password
phpbb_groups.group_avatar_type
phpbb_profile_fields.field_type
phpbb_profile_fields.field_validation
phpbb_profile_fields_lang.field_type
phpbb_topics.topic_first_poster_name
phpbb_users.user_timezone
phpbb_users.user_avatar_type

The Default Value is ('''') when it should be ('')

I've upgraded from 3.0.12 to 3.1.7. And other user upgrade from 3.0.x to 3.1.3 with the same issue.

More information: https://www.phpbb.com/community/viewtopic.php?f=466&t=2296166&p=14395641#p14395641