Update scores/nb_pesq.py

scores/nb_pesq.py

@@ -10,6 +10,6 @@ class NB_PESQ(ScoreBasis):
     def windowed_scoring(self, audios, score_rate):
         from pesq import pesq
         if len(audios) != 2:
-            raise ValueError('PESQ needs a reference and a test signals.')
+            return None
         return pesq(score_rate, audios[1], audios[0], 'nb')