Bug when duplicating existing voucher

[milanjandric]

Description
If you try to duplicate an existing voucher using the save option "Save as new voucher" an Internal Server Error occurs due to the Integrity constraint validation on the voucher SKU field in the giftvouchers_vouchers table.

Steps to reproduce

1. Create a new voucher.
2. Click "Save as new voucher"

Additional info

• Plugin version: 2.5.5
• Craft version: Craft Pro 3.5.11.1
• Multi-site: Yes

[engram-design]

I can't seem to immediately replicate this. It should create the same voucher, but be disabled. This is so the voucher element can be created, with the same identical SKU, but in order to enable it, you need to fix the duplicate SKU.