import re


def find_next_nothing(file_contents):
    """
    Find the next 'nothing' in a string containing the text 'Next nothing is
    <number>'. If this format doesn't exist in the given file contents,
    return None.
    """
    m = re.search('Next nothing is ([0-9]+)', file_contents)
    if m:
        return int(m.group(1))