This PR fixes a bug which has been introduced in the PR #409.
Before the fix, infinite loops happened after parsing a final empty block scalar since updating current position was missed in the lexer.
The above issue can be reproduced by trying to parse the following YAML:

# https://github.com/yaml/yaml-test-suite/blob/data-2022-01-17/JEF9/00/in.yaml
- |+

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