fix: detokenization case where first token does not start with a leading space (#1375)

* Fix tokenization edge case where llama output does not start with a space

See this notebook:
https://colab.research.google.com/drive/1Ooz11nFPk19zyJdMDx42CeesU8aWZMdI#scrollTo=oKpHw5PZ30uC

* Update _internals.py

Fixing to compare to b' ' instead of (str)' '

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Co-authored-by: Andrei <abetlen@gmail.com>