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.
const loadingTask = getDocument(buildGetDocumentParams("issue6106.pdf"));
      const pdfDoc = await loadingTask.promise;
      const javascript = await pdfDoc.getJavaScript();
      expect(javascript).toEqual([
        "this.print({bUI:true,bSilent:false,bShrinkToFit:true});",
      ]);
      expect(javascript[0]).toMatch(AutoPrintRegExp);
      await loadingTask.destroy();
    });
    it("gets hasJSActions, in document without javaScript", async function () {
      const hasJSActions = await pdfDocument.hasJSActions();
      expect(hasJSActions).toEqual(false);
    });
    it("gets hasJSActions, in document with javaScript", async function () {
      const loadingTask = getDocument(
        buildGetDocumentParams("doc_actions.pdf")
      );
      const pdfDoc = await loadingTask.promise;
      const hasJSActions = await pdfDoc.hasJSActions();
      expect(hasJSActions).toEqual(true);
      await loadingTask.destroy();
    });
    it("gets non-existent JSActions", async function () {
      const jsActions = await pdfDocument.getJSActions();
      expect(jsActions).toEqual(null);
    });
    it("gets JSActions", async function () {
      
      const loadingTask = getDocument(
        buildGetDocumentParams("doc_actions.pdf")