React 0.14.7: `<option value="">empty</option>` emits empty string on change
http://jsbin.com/pisita/10/edit?html,js,console,output
React 15.0.0-rc.1`<option value="">empty</option>` emits string with value "empty" on change
http://jsbin.com/bemaze/12/edit?html,js,console,output
This is because React 15.0.0-rc.1 cuts off `value=""` from option tag

didWarnValueLink = true;
      }
      if (props.checkedLink !== undefined && !didWarnCheckedLink) {
        warning(
          false,
          '`checkedLink` prop on `input` is deprecated; set `value` and `onChange` instead.'
        );
        didWarnCheckedLink = true;
      }
      if (
        props.checked !== undefined &&
        props.defaultChecked !== undefined &&
        !didWarnCheckedDefaultChecked
      ) {
        warning(
          false,
          '%s contains an input of type %s with both checked and defaultChecked props. ' +
          'Input elements must be either controlled or uncontrolled ' +
          '(specify either the checked prop, or the defaultChecked prop, but not ' +
          'both). Decide between using a controlled or uncontrolled input ' +
          'element and remove one of these props. More info: ' +
          'https://fb.me/react-controlled-components',
          owner && owner.getName() || 'A component',
          props.type
        );
        didWarnCheckedDefaultChecked = true;
      }
      if (
        props.value !== undefined &&
        props.defaultValue !== undefined &&