_onUrlInputChange(e) {
    e.stopPropagation();

    if (!e.target) {
      return;
    }

    const inputElement = /** @type {HTMLInputElement} */ (e.target);

    try {
      this._loadFromGistURL(inputElement.value);
    } catch (err) {
      logger.error('Invalid URL');
    }
  }
Handles changes to the gist url input.
@param {Event} e
@private