message: Fix dark theme styling of roomheader cancel button
diff: @@ -26,7 +26,8 @@ export function CancelButton(props) {
  return (
  <AccessibleButton className='mx_RoomHeader_cancelButton' onClick={onClick}>
  - <img src="img/cancel.svg" width="18" height="18" alt="Cancel"/>
  + <img src="img/cancel.svg" className='mx_filterFlipColor'
  + width="18" height="18" alt="Cancel"/>
  </AccessibleButton>
  );
  }
  