[Select] Set type undefined rather than null

[caub]

continuation of #10361 (comment)

I couldn't use defaultProps for type,
If I put a

SelectInput.defaultProps = {
  type: undefined,
};

and remove = 'hidden' in render

test:unit fails with:

1) <Select> integration
       with Dialog
         should focus the selected item:
     Error: Uncaught [Error: Warning: Failed prop type: You provided a `value` prop to a form field without an `onChange` handler. This will render a read-only field. If the field should be mutable use `defaultValue`. Otherwise, set either `onChange` or `readOnly`

---

note: would you like to refactor all components, and define propTypes and defaultProps as static properties at the start of component class?
If you want them at the end, still possible too:

class SelectInput extends React.Component {
  static propTypes = propTypes;
  state = {
    open: false,
  };
  // ...

} 

const propTypes = {
  //..
};

[oliviertassinari]

Interesting, what do we win from this change?

[caub]

not much :), it allows to force it to null, and I find destructuring defaults clearer personally. But if you do <Select type={null} it will stay as null

[oliviertassinari]

@caub Alright, let's try that :)