fix bug (#2200)

* fix bug

* fix bug

* fix lint

* fix bug

* revert the modification

* fix lint

* fix bug

* fix bug

* fix bug

Author: manbaaaa

wenet/transformer/asr_model.py

@@ -50,8 +50,16 @@ def __init__(
 
         super().__init__()
         # note that eos is the same as sos (equivalent ID)
-        self.sos = special_tokens.get("sos", vocab_size - 1)
-        self.eos = special_tokens.get("eos", vocab_size - 1)
+        self.sos = (
+            vocab_size - 1
+            if special_tokens is None
+            else special_tokens.get("sos", vocab_size - 1)
+        )
+        self.eos = (
+            vocab_size - 1
+            if special_tokens is None
+            else special_tokens.get("eos", vocab_size - 1)
+        )
         self.vocab_size = vocab_size
         self.special_tokens = special_tokens
         self.ignore_id = ignore_id