anchor.diff:     * not added if the [value] is equal to [def].
      */
     void addInt64(int field, int value, [int def]) {
  -    if (_currentVTableBuilder == null) {
  +    if (_currentVTable == null) {
         throw new StateError('Start a table before adding values.');
       }
       if (value != def) {
  
positive.code:     buf.setUint16(bufOffset, tableSize, Endianness.LITTLE_ENDIAN);
      bufOffset += 2;
      // Field offsets.
      for (int fieldTail in fieldTails) {
        int fieldOffset = fieldTail == null ? 0 : tableTail - fieldTail;
        buf.setUint16(bufOffset, fieldOffset, Endianness.LITTLE_ENDIAN);
        bufOffset += 2;
      }
  
negative.code:    * not added if the [value] is equal to [def].
     */
    void addInt8(int field, int value, [int def]) {
      if (_currentVTable == null) {
        throw new StateError('Start a table before adding values.');
      }
      if (value != def) {
  