Localization: the error about language switcher

This issue is based on this repository “Headless Multilingual Starter for Gatsby 4 with DatoCMS”.

I unchecked the All locales required? option[1] in the model settings and published the only Italy version post.
But the other language options still show up on the header. When I clicked the other language, the error comes out like the below screenshot[2]. I guess that it is failed to query data of other language.
In this case, how should I fix the code or setting on datocms console ?

[1]

[2]

Thank you,

Hello @JJ

You can remove (or add) certain locales from a record by following the following video: Screen Recording 2022-01-24 at 10.52.47

As for the project, i’m trying to install it to help you debug it, but i’m encountering some problems with it.
It isn’t a project directly maintained by Dato (you can see demo projects directly maintained by Dato here: Project starters - Free demo projects - Marketplace
So i can’t guarantee support for it, but i’ll try getting in contact with the project creator to see if we can find a solution.