Fix TypeError on list-typed ignore_keys_at_rope_validation in RoPE config (#46142)
* Fix TypeError in convert_rope_params_to_dict when ignore_keys_at_rope_validation is a list
* Handle None in ignore_keys_at_rope_validation coercion
* Apply suggestion
Co-authored-by: Anton Vlasjuk <73884904+vasqu@users.noreply.github.com>
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Co-authored-by: Anton Vlasjuk <73884904+vasqu@users.noreply.github.com>