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.
} else {
          affectedBoundary.x2New = maxXNew;
        }
      } else if (affectedBoundary.x2New > maxXNew) {
        
        affectedBoundary.x2New = Math.max(maxXNew, affectedBoundary.x2);
      }
    }
    
    const changedHorizon = [];
    let lastBoundary = null;
    for (q = i; q <= j; q++) {
      horizonPart = horizon[q];
      affectedBoundary = horizonPart.boundary;
      
      const useBoundary =
        affectedBoundary.x2 > boundary.x2 ? affectedBoundary : boundary;
      if (lastBoundary === useBoundary) {
        
        changedHorizon[changedHorizon.length - 1].end = horizonPart.end;
      } else {
        changedHorizon.push({
          start: horizonPart.start,
          end: horizonPart.end,
          boundary: useBoundary,
        });
        lastBoundary = useBoundary;
      }
    }
    if (horizon[i].start < boundary.y1) {