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 horizon = [
    {
      start: -Infinity,
      end: Infinity,
      boundary: fakeBoundary,
    },
  ];
  for (const boundary of bounds) {
    
    
    let i = 0;
    while (i < horizon.length && horizon[i].end <= boundary.y1) {
      i++;
    }
    let j = horizon.length - 1;
    while (j >= 0 && horizon[j].start >= boundary.y2) {
      j--;
    }
    let horizonPart, affectedBoundary;
    let q,
      k,
      maxXNew = -Infinity;
    for (q = i; q <= j; q++) {
      horizonPart = horizon[q];
      affectedBoundary = horizonPart.boundary;
      let xNew;
      if (affectedBoundary.x2 > boundary.x1) {