fixed no candidate exception

Giveme5W1H/extractor/candidate.py

@@ -23,6 +23,9 @@ def set_parts(self, parts):
         self._parts = parts
 
     def get_parts_as_text(self):
+        if not self._parts:
+            return "No result can be found in the document."
+
         answer_text = []
         for part in self._parts:
             answer_text.append(part[0]['nlpToken']['originalText'])

Giveme5W1H/extractor/document.py

@@ -1,3 +1,4 @@
+from .candidate import Candidate
 class Document(object):
     """
     Document is a pickable container for the raw document and all related data
@@ -148,7 +149,11 @@ def get_answers(self, question=None):
             return self._answers
 
     def get_top_answer(self, question):
-        return self.get_answers(question=question)[0]
+        answers = self.get_answers(question=question)
+        if len(answers) == 0:
+            return Candidate()
+        else:
+            return answers[0]
 
     def get_annotations(self):
         return self._annotations