input: Write a function to select all rows from a table where the 'status' is 'approved'. If the 'status' column is empty or does not exist, return an empty list.
  assert select_approved_rows() == [('item1', 'approved'), ('item2', 'approved')]
  assert select_approved_rows() == []
  assert select_approved_rows() == [('item3', 'approved')]
output: def select_approved_rows(table=None):
      if not table or 'status' not in table[0]:
          return []
      return [row for row in table if row['status'] == 'approved']