Ignore not initialized NO_CONFIG_TOKENIZERs (#10936)

src/transformers/models/auto/tokenization_auto.py

@@ -288,7 +288,7 @@ def tokenizer_class_from_name(class_name: str):
     all_tokenizer_classes = (
         [v[0] for v in TOKENIZER_MAPPING.values() if v[0] is not None]
         + [v[1] for v in TOKENIZER_MAPPING.values() if v[1] is not None]
-        + NO_CONFIG_TOKENIZER
+        + [v for v in NO_CONFIG_TOKENIZER if v is not None]
     )
     for c in all_tokenizer_classes:
         if c.__name__ == class_name: