update rec_sar_head

ppocr/modeling/heads/rec_sar_head.py

@@ -151,7 +151,7 @@ class ParallelSARDecoder(BaseDecoder):
                 **kwargs):
         super().__init__()
 
-        self.num_classes = num_classes
+        self.num_classes = out_channels
         self.enc_bi_rnn = enc_bi_rnn
         self.d_k = d_k
         self.start_idx = out_channels - 2