chore: limit should be greater than 0

[codecov-commenter]

Codecov Report

Base: 77.55% // Head: 77.55% // Decreases project coverage by -0.00% :warning:

Coverage data is based on head (590ac55) compared to base (f892479). Patch coverage: 75.00% of modified lines in pull request are covered.

Additional details and impacted files

```diff @@ Coverage Diff @@ ## develop #103 +/- ## =========================================== - Coverage 77.55% 77.55% -0.01% =========================================== Files 23 23 Lines 4630 4637 +7 =========================================== + Hits 3591 3596 +5 - Misses 1039 1041 +2 ``` | Flag | Coverage Δ | | |---|---|---| | unittests | `77.55% <75.00%> (-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=nervosnetwork#carryforward-flags-in-the-pull-request-comment) to find out more. | [Impacted Files](https://codecov.io/gh/nervosnetwork/ckb-light-client/pull/103?src=pr&el=tree&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=nervosnetwork) | Coverage Δ | | |---|---|---| | [src/service.rs](https://codecov.io/gh/nervosnetwork/ckb-light-client/pull/103/diff?src=pr&el=tree&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=nervosnetwork#diff-c3JjL3NlcnZpY2UucnM=) | `66.33% <75.00%> (+0.04%)` | :arrow_up: | Help us with your feedback. Take ten seconds to tell us [how you rate us](https://about.codecov.io/nps?utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=nervosnetwork). Have a feature suggestion? [Share it here.](https://app.codecov.io/gh/feedback/?utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=nervosnetwork)

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