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.
await worker.promise;
      expect(worker.name).toEqual("test1");
      expect(!!worker.port).toEqual(true);
      expect(worker.destroyed).toEqual(false);
      expect(!!worker._webWorker).toEqual(true);
      expect(worker.port === worker._webWorker).toEqual(true);
      worker.destroy();
      expect(!!worker.port).toEqual(false);
      expect(worker.destroyed).toEqual(true);
    });
    it("worker created or destroyed by getDocument", async function () {
      if (isNodeJS) {
        pending("Worker is not supported in Node.js.");
      }
      const loadingTask = getDocument(basicApiGetDocumentParams);
      let worker;
      loadingTask.promise.then(function () {
        worker = loadingTask._worker;
        expect(!!worker).toEqual(true);
      });
      const destroyPromise = loadingTask.promise.then(function () {
        return loadingTask.destroy();
      });
      await destroyPromise;
      const destroyedWorker = loadingTask._worker;
      expect(!!destroyedWorker).toEqual(false);
      expect(worker.destroyed).toEqual(true);
    });
    it("worker created and can be used in getDocument", async function () {
      if (isNodeJS) {