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.
).toEqual(true);
        const passwordIncorrectLoadingTask = getDocument(
          buildGetDocumentParams(filename, {
            password: "qwerty",
          })
        );
        expect(
          passwordIncorrectLoadingTask instanceof PDFDocumentLoadingTask
        ).toEqual(true);
        let passwordNeededDestroyed;
        passwordNeededLoadingTask.onPassword = function (callback, reason) {
          if (reason === PasswordResponses.NEED_PASSWORD) {
            passwordNeededDestroyed = passwordNeededLoadingTask.destroy();
            return;
          }
          
          expect(false).toEqual(true);
        };
        const result1 = passwordNeededLoadingTask.promise.then(
          function () {
            
            expect(false).toEqual(true);
            return Promise.reject(new Error("loadingTask should be rejected"));
          },
          function (reason) {
            expect(reason instanceof PasswordException).toEqual(true);
            expect(reason.code).toEqual(PasswordResponses.NEED_PASSWORD);
            return passwordNeededDestroyed;
          }
        );