resi_header_style function not found

Hello.
My blog started experiencing a warning message in homepage. As it seems, the call_user_func_array looks for a resi_header_style function but it seems it’s not defined anywhere.
My theme was perfectly working a few days ago and I didn’t change any setting.
Moreover, I already tried deactivating all the plugins in bulk but it didn’t change anything. I was looking for the incriminated string in the code but I only can find it in functions.php, that’s where it’s recalled.
Where’s the bug?

Thanks.

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