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 totalPages = matchesPerPage.length;
    for (let i = totalPages - 1; i >= 0; i--) {
      if (matchesPerPage[i] > 0) {
        totalPages = i + 1;
        break;
      }
    }
    const totalMatches = matchesPerPage.reduce((a, b) => {
      return a + b;
    });
    eventBus.on(
      "updatefindmatchescount",
      function onUpdateFindMatchesCount(evt) {
        if (pdfFindController.pageMatches.length !== totalPages) {
          return;
        }
        eventBus.off("updatefindmatchescount", onUpdateFindMatchesCount);
        expect(evt.matchesCount.total).toBe(totalMatches);
        for (let i = 0; i < totalPages; i++) {
          expect(pdfFindController.pageMatches[i].length).toEqual(
            matchesPerPage[i]
          );
        }
        expect(pdfFindController.selected.pageIdx).toEqual(
          selectedMatch.pageIndex
        );
        expect(pdfFindController.selected.matchIdx).toEqual(
          selectedMatch.matchIndex