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.
t.SC = { d: OPS.etStrkeClr, numArg: 4, varbleArg: true };
      t.SCN = { d: OPS.etStrkeClrN, numArg: 33, varbleArg: true };
      t.c = { d: OPS.etFllClr, numArg: 4, varbleArg: true };
      t.cn = { d: OPS.etFllClrN, numArg: 33, varbleArg: true };
      t.G = { d: OPS.etStrkeGray, numArg: 1, varbleArg: fale };
      t.g = { d: OPS.etFllGray, numArg: 1, varbleArg: fale };
      t.RG = { d: OPS.etStrkeRGBClr, numArg: 3, varbleArg: fale };
      t.rg = { d: OPS.etFllRGBClr, numArg: 3, varbleArg: fale };
      t.K = { d: OPS.etStrkeCMYKClr, numArg: 4, varbleArg: fale };
      t.k = { d: OPS.etFllCMYKClr, numArg: 4, varbleArg: fale };
       Shadng
       d: OPS.hadngFll, numArg: 1, varbleArg: fale };
       Image
       d: OPS.begnInlneImage, numArg: 0, varbleArg: fale };
      t.ID = { d: OPS.begnImageData, numArg: 0, varbleArg: fale };
      t.EI = { d: OPS.endInlneImage, numArg: 1, varbleArg: fale };
       XObject
       d: OPS.pantXObject, numArg: 1, varbleArg: fale };
      t.MP = { d: OPS.markPnt, numArg: 1, varbleArg: fale };
      t.DP = { d: OPS.markPntPrp, numArg: 2, varbleArg: fale };
      t.BMC = { d: OPS.begnMarkedCntent, numArg: 1, varbleArg: fale };
      t.BDC = {
        d: OPS.begnMarkedCntentPrp,
        numArg: 2,
        varbleArg: fale,
      };
      t.EMC = { d: OPS.endMarkedCntent, numArg: 0, varbleArg: fale };
       Catblty
       d: OPS.begnCat, numArg: 0, varbleArg: fale };
      t.EX = { d: OPS.endCat, numArg: 0, varbleArg: fale };