Internal link script

const addLinks = (searchPhrase, hyperlink) => {
    const document = DocumentApp.getActiveDocument();
    const body = document.getBody();
    let search = null;
    let count = 0;
    while (count < 1 && (search = body.findText(searchPhrase, search))) {
        const searchElement = search.getElement();
        const startIndex = search.getStartOffset();
        const endIndex = search.getEndOffsetInclusive();
        searchElement.asText().setLinkUrl(startIndex, endIndex, hyperlink);
        count++;
    }
    document.saveAndClose();
};

addLinks("Kiton", "https://2men.it/collections/kiton/");
function addLinksFromSheet() {
  var sheet = SpreadsheetApp.openById("YOUR_SPREADSHEET_ID").getSheetByName("Sheet1");
  var data = sheet.getDataRange().getValues();

  var document = DocumentApp.getActiveDocument();
  var body = document.getBody();

  for (var i = 0; i < data.length; i++) {
    var searchPhrase = data[i][0];
    var hyperlink = data[i][1];

    var search = null;
    var count = 0;
    while (count < 1 && (search = body.findText(searchPhrase, search))) {
      var searchElement = search.getElement();
      var startIndex = search.getStartOffset();
      var endIndex = search.getEndOffsetInclusive();
      searchElement.asText().setLinkUrl(startIndex, endIndex, hyperlink);
      count++;
    }
  }

  document.saveAndClose();
}

Code on top is an upgrade in case one would like to create a database in google sheet of the searchPhrase/Hyperlink and use them automatically in multiple blog articles.
How does that work could you break it down for me?

You add all your articles to one google sheet and then run the code?
The code is not working, I don't know what I am missing, is giving me the error:
Error
Exception: Invalid argument: searchPattern
addLinks	@ Code.gs:6

Any idea of what I can do to fix it?

Thank you!
Replace with this code:

const addLinks = (searchPhrase, hyperlink) => {
    if (!searchPhrase) {
        return;
    }

    const document = DocumentApp.getActiveDocument();
    const body = document.getBody();
    let search = null;
    let count = 0;

    while (count < 1) {
        search = body.findText(searchPhrase, search ? search : null);
        if (!search) {
            break;
        }
        const searchElement = search.getElement();
        const startIndex = search.getStartOffset();
        const endIndex = search.getEndOffsetInclusive();
        searchElement.asText().setLinkUrl(startIndex, endIndex, hyperlink);
        count++;
    }

    document.saveAndClose();
};