Attach (recommended) or Link to PDF file here:  [test.pdf](https://akmer.aikucun.com/a94a8fe5ccb19ba61c4c0873d391e987982fbbd3_1616477914120_83.pdf)


Configuration:
- Web browser and its version: chrome 87.0.4280.88
- Operating system and its version: windows10
- PDF.js version: 2.6.347
- Is a browser extension:

Steps to reproduce the problem:
1. just open 

What is the expected behavior? (add screenshot)

What went wrong? (add screenshot)
![image](https://user-images.githubusercontent.com/17724610/112087066-473f8f80-8bc8-11eb-8efb-56139ec42a9c.png)

Link to a viewer (if hosted on a site other than mozilla.github.io/pdf.js or as Firefox/Chrome extension):

case 2:
        for (i = 0; i < rowBytes; ++i) {
          buffer[j++] = (prevRow[i] + rawBytes[i]) & 0xff;
        }
        break;
      case 3:
        for (i = 0; i < pixBytes; ++i) {
          buffer[j++] = (prevRow[i] >> 1) + rawBytes[i];
        }
        for (; i < rowBytes; ++i) {
          buffer[j] =
            (((prevRow[i] + buffer[j - pixBytes]) >> 1) + rawBytes[i]) & 0xff;
          j++;
        }
        break;
      case 4:
        
        
        for (i = 0; i < pixBytes; ++i) {
          up = prevRow[i];
          c = rawBytes[i];
          buffer[j++] = up + c;
        }
        for (; i < rowBytes; ++i) {
          up = prevRow[i];
          var upLeft = prevRow[i - pixBytes];
          var left = buffer[j - pixBytes];
          var p = left + up - upLeft;
          var pa = p - left;
          if (pa < 0) {