So I have a form with one select (user_id), one input (year) and form to upload PDF document
I made a custom validation using watch from React Hook Form. The problem is that there is a TS error
Property ‘unsubscribe’ does not exist on type ‘readonly (string | File | { file: File; title: string; } | { file: File; title: string; }[])[]’.
What could be the reason ?

type TaxDocumentsFormType = {
    user_id: string;
    year: string;
    tax_doc: { file: File; title: string }[];
};

    const {
        handleSubmit,
        setValue,
        control,
        register,
        getValues,
        watch,
        formState: { isSubmitting, errors },
    } = useForm<TaxDocumentsFormType>({
        defaultValues: {
            year: '',
            tax_doc: [],
        },
        mode: 'onChange',
    });

    useEffect(() => {
        const subscription = watch(
            ({ year, user_id, tax_doc }: TaxDocumentsFormType) => {
                const yearIsValid = YEAR_REGEX.test(year);
                const investorIsValid = user_id !== '';
                const documentIsValid = tax_doc && tax_doc.length > 0;
                setFormIsValid(
                    yearIsValid && investorIsValid && documentIsValid
                );
            }
        );

        return () => {
            subscription.unsubscribe();
        };
    }, [watch]);