It's just a little inconvenience, but if you click the [Add Inventory] button, then get distracted or realize you don't have all the information you need, abandoning the new item without entering ANYTHING, the system will still insert a new blank inventory record. A good test for a valid inventory record is at least a title (or the artist name). Checking for even a SINGLE field value specified should be a good indication of a valid record before insertion in the database.