is_double method Null safety

Implementation

bool is_double() {
  final constructor =
      _dll_handle.lookupFunction<_Context_isDouble_c, _Context_isDouble_dart>(_context_namespace + 'isDouble');
  final exception = _getException();
  bool res = constructor(this._impl, exception);

  tdvCheckException(exception, _dll_handle);

  return res;
}