message: fail command with empty locator
diff: @@ -35,7 +35,7 @@ const createEventObject = window.global.createEventObject;
  const absolutify = window.global.absolutify;
  const addLoadListener = window.global.addLoadListener;
  const highlight = window.global.highlight;
  -const parse_locator = window.global.parse_locator;
  +const _parse_locator = window.global.parse_locator;
  const eval_xpath = window.global.eval_xpath;
  const eval_css = window.global.eval_css;
  const PatternMatcher = window.global.PatternMatcher;
  @@ -51,6 +51,14 @@ const serializeObject = window.global.serializeObject;
  window.global.browserVersion = new window.global.BrowserVersion();
  +function parse_locator(...args) {
  + if (!args[0]) {
  + throw new TypeError("Locator cannot be empty");
  + } else {
  + return _parse_locator(...args);
  + }
  +}
  +
  // The window to which the commands will be sent. For example, to click on a
  // popup window, first select that window, and then do a normal click command.
  export default class BrowserBot {
  