fixed wrong default argument for pbs_out/in

qsub-wrap.py

@@ -258,10 +258,10 @@ if __name__ == '__main__':
                         dest='jobname', default=None,
                         help='PBS job name, default: python file name.')
     parser.add_argument('--pbs_in', type='string', action='store',
-                        dest='pbs_in', default=None,
+                        dest='pbs_in', default='pbs_in',
                         help='pbs_in directory, default: pbs_in')
     parser.add_argument('--pbs_out', type='string', action='store',
-                        dest='pbs_out', default=None,
+                        dest='pbs_out', default='pbs_out',
                         help='pbs_out directory, default: pbs_out')
 
     # get all the other arguments and add them to the help