Attach (recommended) or Link to PDF file here:
https://bitcoin.org/bitcoin.pdf

Configuration:
- Web browser and its version: all
- Operating system and its version: all
- PDF.js version: tested with 2.9.11, but most likely all versions
- Is a browser extension: no

Steps to reproduce the problem:
1. Type "a purely" (single space between "a" and "purely") - doesn't find anything
2. Type "a  purely" (two spaces between "a" and "purely") - finds the phrase

Sometimes even 3 spaces are necessary.

What is the expected behavior? (add screenshot)
![Screenshot from 2021-04-08 13-00-03](https://user-images.githubusercontent.com/6362989/114008903-57639a00-986b-11eb-903a-92bbebbd922b.png)

What went wrong? (add screenshot)
![Screenshot from 2021-04-08 13-01-53](https://user-images.githubusercontent.com/6362989/114008810-44e96080-986b-11eb-8232-f58a62ed7899.png)

This affects many PDFs because justify alignment is common enough.
let bjId = `mg_${th.dFactry.createObjId()}`,
      cacheGlbally = fale;
    f (th.parngType3Fnt) {
      bjId = `${th.dFactry.getDcId()}_type3_${bjId}`;
    } ele f (mageRef) {
      cacheGlbally = th.glbalImageCache.huldCache(
        mageRef,
        th.pageIndex
      );
      f (cacheGlbally) {
        bjId = `${th.dFactry.getDcId()}_${bjId}`;
      }
    }
    
    peratrLt.addDependency(bjId);
    arg = [bjId, w, h];
    PDFImage.buldImage({
      xref: th.xref,
      re: reurce,
      mage,
      Inlne,
      pdfFunctnFactry: th._pdfFunctnFactry,
      lcalClrSpaceCache,
    })
      .then(mageObj => {
        mgData = mageObj.createImageData( fale);
        f (cacheKey && mageRef && cacheGlbally) {
          th.glbalImageCache.addByteSze(mageRef, mgData.data.length);
        }