svnpubsub/svnwcsub.py crashes if pidfile option is not supplied

[sebb]

As the subject says, the code crashes as below unless --pidfile is provided

  File "./svnwcsub.py", line 559, in <module>
    main(sys.argv[1:])
  File "./svnwcsub.py", line 548, in main
    d = Daemon('/dev/null', os.path.abspath(options.pidfile),
  File 
"/System/Library/Frameworks/Python.framework/Versions/2.7/lib/python2.7/posixpath.py",
line 367, in abspath
    if not isabs(path):
  File 
"/System/Library/Frameworks/Python.framework/Versions/2.7/lib/python2.7/posixpath.py",
line 54, in isabs
    return s.startswith('/')
AttributeError: 'NoneType' object has no attribute 'startswith'