tiddlerExists = tiddler => {

  if (!tiddler) {
    return false;
  }

  const tRef = getTiddlerRef(tiddler);

  return Boolean(tRef && ($tw.wiki.tiddlerExists(tRef) || $tw.wiki.isShadowTiddler(tRef)));

}
Checks if tiddlers (including shadow tiddlers) exist.

@param {Tiddler} tiddler
@return {boolean} True if the tiddler exists, false otherwise