[3.10] bpo-47117: Don't crash if we fail to decode characters when the tokenizer buffers are uninitialized (GH-32129) (GH-32130)

Automerge-Triggered-By: GH:pablogsal.
(cherry picked from commit 26cca8067bf5306e372c0e90036d832c5021fd90)

Co-authored-by: Pablo Galindo Salgado <Pablogsal@gmail.com>