Can't place Order ( Internal Server Error )

[owadud]

Describe the bug

Something is not working properly. Internal server error showing on front-end and order is placed on back-end without serial key.

To Reproduce Steps to reproduce the behavior:

1. Go to 'Add key' and create a key.
2. Enable the serial key for that product.
3. Now try to place an order.
4. See the error

Also, if we try to add a key to that product by "Add serial key" from bulk action, it shows a fatal arrow.

[owadud]

fixed