Problems with the opencart template, an error occurs after editing the product?

Question

opencart

I installed the template, uploaded demo data. When editing a product, an error occurs when saving
- Notice: Undefined index: length_class_id in /home/c/cj65610/storage/modification/admin/model/catalog/product.php on line 141Warning: Cannot modify header information - headers already sent by (output started at /home/c/cj65610/public_html/admin/controller/startup/error.php:34) in /home/c/cj65610/public_html/system/library/response.php on line 36
What is the reason for this? Although the changes are saved, this error always follows.

Answer 1

Have you tried using a translator if you don't know English yourself? It is written: Undefined index: length_class_id