Can't add zero cost into maintenance log

Hello!

It is not possible to set zero cost to maintenance log. I have vehicle that had a free quality enchantment campaign and it would be great to log that maintence.

Error:

<img width="390" height="357" alt="Image" src="https://github.com/user-attachments/assets/12fbb779-49c2-4fa1-a684-8119119711b0" />