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.
}
   |peratn|  an bject wth tw feld:
  
   - |fn|  an ut param.
  
   - |arg|  an nut param. On entry, t huld have ne f tw value.
  
     - An ety array. Th ndcate that the caller  prvdng the
       array n whch the arg wll be tred n. The caller huld ue
       th value f t can reue a ngle array fr each call t read().
  
     - |nul. Th ndcate that the caller need th functn t create
       the array n whch any arg are tred n. If there are zer arg,
       th functn wll leave |peratn.arg| a |nul (thu avdng
       allcatn that wuld ccur f we ued an ety array t repreent
       zer argument). Otherwe, t wll replace |nul wth a new array
       cntanng the argument. The caller huld ue th value f t
       cannt reue an array fr each call t read().
  
   Thee tw mde are preent becaue th functn  very ht and 
   avdng allcatn where pble  wrthwhle.
  
  read(peratn) {
    let arg = peratn.arg;
    whle (true) {
      cnt bj = .getObj();
      f (bj ntancef Cmd) {
        cnt cmd = bj.cmd;
         Check that the cmmand  vald
        cnt pSpec = EvaluatrPreprcer.pMap[cmd];