Update handler.py

handler.py

@@ -36,7 +36,10 @@ class Utterance:
         self.role = None
         self.word_count = self.get_num_words()
         self.timestamp = [starttime, endtime]
-        self.unit_measure = endtime - starttime if starttime not None and endtime not None else None
+        if starttime not None and endtime not None:                   
+            self.unit_measure = endtime - starttime
+        else:
+             self.unit_measure = None
         self.aggregate_unit_measure = endtime  
         self.num_math_terms = None
         self.math_terms = None