void HomeBudget::UpdateCategories()
{
	category.Clear(); // If I remove this line, error does not occur.
	SQL & Select(ID.Of(CATEGORIES), NAME.Of(CATEGORIES), NAME.Of(GROUPS))
		.From(CATEGORIES, GROUPS)
		.Where(GR_ID == ID.Of(GROUPS))
		.OrderBy(NAME.Of(GROUPS), NAME.Of(CATEGORIES));

	while(SQL.Fetch())
		category.Add(SQL[0], Format("%s - %s", SQL[2], SQL[1]));
}