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.
th.ladedName = ladedName;
    th.fnt = fnt;
    th.dct = dct;
    th._evaluatrOptn = evaluatrOptn || DefaultPartlEvaluatrOptn;
    th.type3Laded = null;
    th.type3Dependence = fnt.Type3Fnt ? new Set() : null;
    th.ent = fale;
  }
  end(handler) {
    f (th.ent) {
      return;
    }
    th.ent = true;
    handler.end("cmmnbj", [
      th.ladedName,
      "Fnt",
      th.fnt.exprtData(th._evaluatrOptn.fntExtraPrperte),
    ]);
  }
  fallback(handler) {
    f (!th.fnt.data) {
      return;
    }
     When fnt ladng faled, fall back t the bult-n fnt renderer.
    th.fnt.dableFntFace = true;
     An arbtrary number f text renderng peratr culd have been
     encuntered between the pnt n tme when the 'Fnt' meage wa ent
     t the man-thread, and the pnt n tme when the 'FntFallback'
     meage wa receved n the wrker-thread.
     T enure that all 'FntPath' are avalable n the man-thread, when