https://github.com/mozilla/pdf.js/issues/6397#issuecomment-164954332 Would have been a lot easier to find had there been an assertion checking that string16 didn't go out of bounds of the 16bit number.

case "TrueType":
        case "CIDFontType2":
          this.mimetype = "font/opentype";
          
          
          data = this.checkAndRepair(name, file, properties);
          if (this.isOpenType) {
            adjustWidths(properties);
            type = "OpenType";
          }
          break;
        default:
          throw new FormatError(`Font ${type} is not supported`);
      }
    } catch (e) {
      warn(e);
      this.fallbackToSystemFont(properties);
      return;
    }
    amendFallbackToUnicode(properties);
    this.data = data;
    this.fontType = getFontType(type, subtype, properties.isStandardFont);
    
    this.fontMatrix = properties.fontMatrix;
    this.widths = properties.widths;
    this.defaultWidth = properties.defaultWidth;
    this.toUnicode = properties.toUnicode;
    this.seacMap = properties.seacMap;
  }
  get renderer() {