fix : fallback store in config

[tprelle]

Hi,
Fallback model it's not serialize in the config file so we can not edit it because it's missing from the function

[Ayushkiller]

Looks good and self explanatory

[Adcbda]

Same issue.

[anhnh2002]

Thanks for catching this and sending the fix, @tprelle! 🙏 fallback_model was indeed being silently dropped on save — nice spot.