Google Apps Script. Get all links from document

Question

Hi all) I need to get all links from google document. I found that general approach:

function getAllLinks(element) {
  var links = [];
  element = element || DocumentApp.getActiveDocument().getBody();

  if (element.getType() === DocumentApp.ElementType.TEXT) {
    var textObj = element.editAsText();
    var text = element.getText();

    Logger.log("text " + text);

    var inUrl = false;
    for (var ch=0; ch < text.length; ch++) {
      var url = textObj.getLinkUrl(ch);
      if (url != null) {
        if (!inUrl) {
          // We are now!
          inUrl = true;
          var curUrl = {};
          curUrl.element = element;
          curUrl.url = String( url ); // grab a copy
          curUrl.startOffset = ch;
        }
        else {
          curUrl.endOffsetInclusive = ch;
        }          
      }
      else {
        if (inUrl) {
          // Not any more, we're not.
          inUrl = false;
          links.push(curUrl);  // add to links
          curUrl = {};
        }
      }
    }
  }
  else {
    var numChildren = element.getNumChildren();
    for (var i=0; i<numChildren; i++) {
      links = links.concat(getAllLinks(element.getChild(i)));
    }
  }

  Logger.log(links);
}

It works perfectly fine if i, for example, type url in text, but if add link via menu ("Insert" -> "Link") it doesn't work, function getLinkUrl() returns null. Documentation contains info about Link class, i thought all links represented by it, but don't understand why i can't get link inserted via menu.

I thought maybe i can use some regular expression on text of document element, but if i add link via menu item i can specify custom label for link, which may not contain url in it.

Have anyone faced this scenario? What i missed?