message: just show plus icon when textarea is empty
diff: @@ -127,7 +127,7 @@ export default class MessageBox extends React.PureComponent {
  accessibilityTraits='button'
  onPress={() => this.submit(this.state.text)}
  />);
  - }
  + } else {
  icons.push(<MyIcon
  style={[styles.actionButtons, { color: '#2F343D', fontSize: 16 }]}
  name='plus'
  @@ -136,6 +136,7 @@ export default class MessageBox extends React.PureComponent {
  accessibilityTraits='button'
  onPress={() => this.addFile()}
  />);
  + }
  return icons;
  }
  