Attach (recommended) or Link to PDF file here: https://github.com/tesseract-ocr/tesseract/files/947838/2.pdf

Configuration:
- Web browser and its version: N/A
- Operating system and its version: N/A
- PDF.js version: `2.9.223`, or any version after PR #13306 landed.
- Is a browser extension: N/A

Steps to reproduce the problem:
1. Open the document above, e.g. with https://mozilla.github.io/pdf.js/web/viewer.html
2. Search for "of the r"

What is the expected behavior? (add screenshot)
Correct highlighting, please see:

![correct](https://user-images.githubusercontent.com/2692120/117328223-b7158b00-ae93-11eb-805c-73718ff569b5.png)


What went wrong? (add screenshot)
Incorrect highlighting, please see:

![incorrect](https://user-images.githubusercontent.com/2692120/117328447-efb56480-ae93-11eb-8506-da9fc0eb9630.png)

Link to a viewer (if hosted on a site other than mozilla.github.io/pdf.js or as Firefox/Chrome extension): N/A

/cc @brendandahl 

this.cancel();
    this.textContentStream = readableStream;
  }
  setTextContent(textContent) {
    this.cancel();
    this.textContent = textContent;
  }
  _convertMatches(matches, matchesLength) {
    
    if (!matches) {
      return [];
    }
    const { textContentItemsStr } = this;
    let i = 0,
      iIndex = 0;
    const end = textContentItemsStr.length - 1;
    const result = [];
    for (let m = 0, mm = matches.length; m < mm; m++) {
      
      let matchIdx = matches[m];