[Findit] Filter empty class.

appengine/findit/crash/classifier.py

 # Copyright 2016 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.
 
 from collections import namedtuple
 from collections import OrderedDict
 
 from common import constants
 from crash.type_enums import CallStackLanguageType
 from model.crash.crash_config import CrashConfig
@@ skipping 73 matching lines @@
         if class_name not in infos:
           infos[class_name] = ClassOccurrenceInfo(class_name, [index])
         else:
           infos[class_name].occurrences.append(index)
 
       return infos.values()
 
     class_infos = _GetClassOccurrenceInfos()
     class_infos = sorted(class_infos, key=rank_function)
 
-    classes = [info.name for info in class_infos]
+    # Filter all empty class.
+    classes = [info.name for info in class_infos if info.name]
 
     return classes[:max_classes]
 
   def Classify(self, results, crash_stack):  # pragma: no cover.
     raise NotImplementedError()