if the field code is empty, then we use the field key

Device: Urovo CT58S
Field code is empty

![Image](https://github.com/user-attachments/assets/b7fe10ba-26f1-474a-a5e3-61ba3d3b3ccd)

<img width="852" height="411" alt="Image" src="https://github.com/user-attachments/assets/dd8decfc-b7b2-4204-86e1-1e6ac6b10e2a" />