This is Sandbox environment. And yes, for "Item Category" page, no extensions were deployed. But have deployed Extension for Item card, and it does not refer to "Item Category".
This error started, when i imported few items having "Item Category" as "XYZ" and also imported "Item Category" Master "XYZ" with blank "Parent Category code" using configuration package.
Is this creating an issue?
Issue is still there, even after i have deleted All the imported items and "Item Category" Master.