size method Null safety

Implementation

int size() {
  var exception = _getException();

  int result = _dll_handle.lookupFunction<_DynamicTemplateIndex_size_c, _DynamicTemplateIndex_size_dart>(_c_namespace + "DynamicTemplateIndex_size")(
      _impl, exception);

  checkException(exception, _dll_handle);

  return result;
}