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

props,
        inst._currentElement._owner
      );
      if (props.valueLink !== undefined && !didWarnValueLink) {
        warning(
          false,
          '`valueLink` prop on `textarea` is deprecated; set `value` and `onChange` instead.'
        );
        didWarnValueLink = true;
      }
      if (
        props.value !== undefined &&
        props.defaultValue !== undefined &&
        !didWarnValDefaultVal
      ) {
        warning(
          false,
          'Textarea elements must be either controlled or uncontrolled ' +
          '(specify either the value prop, or the defaultValue prop, but not ' +
          'both). Decide between using a controlled or uncontrolled textarea ' +
          'and remove one of these props. More info: ' +
          'https://fb.me/react-controlled-components'
        );
        didWarnValDefaultVal = true;
      }
      warnIfValueIsNull(props);
    }
    var defaultValue = props.defaultValue;
    
    var children = props.children;