precompiled_charsmap checking before adding to the normalizers' list for...

precompiled_charsmap checking before adding to the normalizers' list for XLNetTokenizerFast conversion. (#24618)

* precompiled_charsmap checking before adding to the normalizers' list.

* precompiled_charsmap checking for all Sentencepiece tokenizer models

* precompiled_charsmap checking for SPM tokenizer models - correct formatting

src/transformers/convert_slow_tokenizer.py

@@ -551,7 +551,10 @@ class AlbertConverter(SpmConverter):
             list_normalizers.append(normalizers.Lowercase())
 
         precompiled_charsmap = proto.normalizer_spec.precompiled_charsmap
+
+        if precompiled_charsmap:
             list_normalizers.append(normalizers.Precompiled(precompiled_charsmap))
+
         list_normalizers.append(normalizers.Replace(Regex(" {2,}"), " "))
         return normalizers.Sequence(list_normalizers)
 
@@ -802,7 +805,10 @@ class XLNetConverter(SpmConverter):
             list_normalizers.append(normalizers.Lowercase())
 
         precompiled_charsmap = proto.normalizer_spec.precompiled_charsmap
+
+        if precompiled_charsmap:
             list_normalizers.append(normalizers.Precompiled(precompiled_charsmap))
+
         list_normalizers.append(normalizers.Replace(Regex(" {2,}"), " "))
         return normalizers.Sequence(list_normalizers)
 
@@ -836,7 +842,10 @@ class RemBertConverter(SpmConverter):
             list_normalizers.append(normalizers.Lowercase())
 
         precompiled_charsmap = proto.normalizer_spec.precompiled_charsmap
+
+        if precompiled_charsmap:
             list_normalizers.append(normalizers.Precompiled(precompiled_charsmap))
+
         return normalizers.Sequence(list_normalizers)
 
     def post_processor(self):