If after an installation or upgrade, you are experiencing one of following errors:
Notice: Undefined variable: i1 in ...\item\tmpl\extrafields_legacy.php on line 151
Unknown column 'required' in 'where clause' SQL=...
Please do the following:
djc2_items_extra_fields table. If not, execute following SQL query, where PREFIX_ is your table prefix.
ALTER TABLE `PREFIX_djc2_items_extra_fields` ADD `required` SMALLINT NOT NULL DEFAULT '0';