Tiny refactor for PR #1451

[codecov[bot]]

Codecov Report

Attention: Patch coverage is 90.47619% with 2 lines in your changes missing coverage. Please review.

Project coverage is 89.78%. Comparing base (acfe33d) to head (6b52f72). Report is 6 commits behind head on master.

Files with missing lines	Patch %	Lines
lark/parsers/earley.py	84.61%	2 Missing :warning:

Additional details and impacted files

```diff @@ Coverage Diff @@ ## master #1459 +/- ## ========================================== - Coverage 89.78% 89.78% -0.01% ========================================== Files 52 52 Lines 7821 7819 -2 ========================================== - Hits 7022 7020 -2 Misses 799 799 ``` | [Flag](https://app.codecov.io/gh/lark-parser/lark/pull/1459/flags?src=pr&el=flags&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=lark-parser) | Coverage Δ | | |---|---|---| | [unittests](https://app.codecov.io/gh/lark-parser/lark/pull/1459/flags?src=pr&el=flag&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=lark-parser) | `89.78% <90.47%> (-0.01%)` | :arrow_down: | Flags with carried forward coverage won't be shown. [Click here](https://docs.codecov.io/docs/carryforward-flags?utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=lark-parser#carryforward-flags-in-the-pull-request-comment) to find out more.

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