message: other: Add config error if default_widget_count is not used with default_widget_type
diff: @@ -613,7 +613,9 @@ fn get_default_widget_and_count(
  Ok((widget_type, widget_count as u64))
  }
  } else {
  - Ok((None, 1))
  + Err(BottomError::ConfigError(
  + "cannot set 'default_widget_count' by itself, it must be used with 'default_widget_type'.".to_string(),
  + ))
  }
  }
  