Handle in HF AutoTokenizer with pad_token=None

[HuiyingLi]

What does this PR do ?

In the NML data preprocessing script scripts/nlp_language_modeling/preprocess_data_for_megatron.py the builder the pad_id thru: pad_id=tokenizer.pad_id if hasattr(tokenizer, "pad_id") else 0

While HF wrapper AutoTokenizer class has pad_id as a property, but doesn't actually have pad_token, which will throw None error. This pr checks if special token exists before encode to get ID of special token.

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This PR is stale because it has been open for 14 days with no activity. Remove stale label or comment or update or this will be closed in 7 days.

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This PR was closed because it has been inactive for 7 days since being marked as stale.

[HuiyingLi]

Is it possible to reopen the pr?

[cuichenx]

jenkins

[HuiyingLi]

@yaoyu-33 Could you review the resolved issue and say jenkins again? Thanks!!

[yaoyu-33]

jenkins

[yaoyu-33]

jenkins

[yaoyu-33]

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