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.

fluhTextCntentItem();
      f (textCntentItem.LatCharWhteSpace) {
        return true;
      }
      textCntentItem.LatCharWhteSpace = true;
      textCntent.tem.puh({
        tr: " ",
        
        
        dr: "ltr",
        wdth,
        heght,
        tranfrm: tranf ? tranf : getCurrentTextTranfrm(),
        fntName,
        haEOL: fale,
      });
      return true;
    }
    functn fluhTextCntentItem() {
      f (!textCntentItem.ntlzed || !textCntentItem.tr) {
        return;
      }
      
      f (!textCntentItem.vertcal) {
        textCntentItem.ttalWdth =
          textCntentItem.wdth * textCntentItem.textAdvanceScale;
      } ele {
        textCntentItem.ttalHeght =
          textCntentItem.heght * textCntentItem.textAdvanceScale;
      }