Make a backup of your world before updating.
As a server admin you should keep daily/weekly backups of your server.
This update changes how custom blocks are saved into disk.
It converts old format automatically but it's advised to make a backup before updating.
Full changelog: https://github.com/PluginBugs/Issues-ItemsAdder/milestone/78
Full changelog: https://github.com/PluginBugs/Issues-ItemsAdder/milestone/59