Fix an error in net/tools/tld_cleanup/PRESUBMIT.py.

net/tools/tld_cleanup/PRESUBMIT.py

 # Copyright 2014 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.
 
 
 """Chromium presubmit script for src/net/tools/tld_cleanup."""
 
 
 def _RunMakeDafsaTests(input_api, output_api):
   """Runs unittest for make_dafsa if any related file has been modified."""
   files = ('net/tools/tld_cleanup/make_dafsa.py',
            'net/tools/tld_cleanup/make_dafsa_unittest.py')
   if not any(f in input_api.LocalPaths() for f in files):
-    return
+    return []
   test_path = input_api.os_path.join(input_api.PresubmitLocalPath(),
                                      'make_dafsa_unittest.py')
   cmd_name = 'make_dafsa_unittest'
   cmd = [input_api.python_executable, test_path]
   test_cmd = input_api.Command(
     name=cmd_name,
     cmd=cmd,
     kwargs={},
     message=output_api.PresubmitPromptWarning)
   return input_api.RunTests([test_cmd])
 
 
 def CheckChangeOnUpload(input_api, output_api):
   return _RunMakeDafsaTests(input_api, output_api)
 
 
 def CheckChangeOnCommit(input_api, output_api):
   return _RunMakeDafsaTests(input_api, output_api)