message: fix null detection result columns
diff: @@ -133,7 +133,7 @@ export default /*public final*/ class PDF417ScanningDecoder {
  let leftToRight: boolean = leftRowIndicatorColumn !== null;
  for (let barcodeColumnCount /*int*/ = 1; barcodeColumnCount <= maxBarcodeColumn; barcodeColumnCount++) {
  let barcodeColumn: int = leftToRight ? barcodeColumnCount : maxBarcodeColumn - barcodeColumnCount;
  - if (detectionResult.getDetectionResultColumn(barcodeColumn) !== null) {
  + if (detectionResult.getDetectionResultColumn(barcodeColumn) !== /* null */ undefined) {
  // This will be the case for the opposite row indicator column, which doesn't need to be decoded again.
  continue;
  }
  