Fix a None reference exception when searching for presubmit scripts.

gcl.py

 #!/usr/bin/python
 # Copyright (c) 2006-2009 The Chromium Authors. All rights reserved.
 # Use of this source code is governed by a BSD-style license that can be
 # found in the LICENSE file.
 
 """\
 Wrapper script around Rietveld's upload.py that simplifies working with groups
 of files.
 """
 
@@ skipping 848 matching lines @@
   if change_info:
     trychange_args.extend(['--name', change_info.name])
     if change_info.issue:
       trychange_args.extend(["--issue", str(change_info.issue)])
     if change_info.patchset:
       trychange_args.extend(["--patchset", str(change_info.patchset)])
     trychange_args.extend(args)
     file_list = change_info.GetFileNames()
   else:
     trychange_args.extend(args)
-    file_list = None
+    file_list = []
   return trychange.TryChange(
       trychange_args,
       file_list=file_list,
       swallow_exception=swallow_exception,
       prog='gcl try',
       extra_epilog='\n'
           'When called from gcl, use the format gcl try <change_name>.\n')
 
 
 @need_change_and_args
@@ skipping 456 matching lines @@
     if e.code != 500:
       raise
     print >> sys.stderr, (
         'AppEngine is misbehaving and returned HTTP %d, again. Keep faith '
         'and retry or visit go/isgaeup.\n%s') % (e.code, str(e))
     return 1
 
 
 if __name__ == "__main__":
   sys.exit(main(sys.argv[1:]))