fix: nested attributes with number as hash key now work

[dsalahutdinov]

This code works ok

ActionController::Parameters.new({"0" => {:subject_id=>45542597, :quantity=>1}}).permit([:subject_id, :quantity])
=> {:subject_id=>45542597, :quantity=>1}

expect number hash key to works ok too, but

ActionController::Parameters.new({0 => {:subject_id=>45542597, :quantity=>1}}).permit([:subject_id, :quantity])
=> {}