my client has updated to the latest version of Joomla: 3.8.1 und K2 to 2.8.0. Frontend and Backend are working, but it is not possible to edit a k2 item or k2 category. List view is working, but not the edit view.
Here a stack trace:
Follow the idea given below, I could find that the cause of the error comes from a custom k2-plugin which I wrote for that client. Within the
xml manifest file of that plugin those defined fields cause the trouble
<field name="lnk_items" type="litems" default="" label="K2_DRAG_AND_DROP_TO_REORDER_ITEMS" description="…"/> <field name="lnk_category" type="lcategoriesmultiple" default="" label="K2_SELECT_ONE_OR_MORE_CATEGORIES" description="…"/>
If I comment out those fields, no error appears, but the plugin cannot work as expected, too.