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.
function (reason) {
          expect(reason instanceof Error).toEqual(true);
        }
      );
      nonIntegerPromise = nonIntegerPromise.then(
        function () {
          throw new Error("shall fail for non-integer pageNumber parameter");
        },
        function (reason) {
          expect(reason instanceof Error).toEqual(true);
        }
      );
      nonNumberPromise = nonNumberPromise.then(
        function () {
          throw new Error("shall fail for non-number pageNumber parameter");
        },
        function (reason) {
          expect(reason instanceof Error).toEqual(true);
        }
      );
      await Promise.all([
        outOfRangePromise,
        nonIntegerPromise,
        nonNumberPromise,
      ]);
    });
    it("gets page, from /Pages tree with circular reference", async function () {
      const loadingTask = getDocument(
        buildGetDocumentParams("Pages-tree-refs.pdf")
      );