Prevent declaration if it was declared earlier

[codecov[bot]]

Codecov Report

Patch coverage: 100.00% and project coverage change: +0.01 :tada:

Comparison is base (3201031) 93.13% compared to head (54e08df) 93.14%.

Additional details and impacted files

```diff @@ Coverage Diff @@ ## master #72 +/- ## ============================================ + Coverage 93.13% 93.14% +0.01% - Complexity 302 303 +1 ============================================ Files 57 57 Lines 932 934 +2 ============================================ + Hits 868 870 +2 Misses 64 64 ``` | [Impacted Files](https://codecov.io/gh/spiral/roadrunner-bridge/pull/72?src=pr&el=tree&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=spiral) | Coverage Δ | | |---|---|---| | [src/Queue/RPCPipelineRegistry.php](https://codecov.io/gh/spiral/roadrunner-bridge/pull/72?src=pr&el=tree&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=spiral#diff-c3JjL1F1ZXVlL1JQQ1BpcGVsaW5lUmVnaXN0cnkucGhw) | `100.00% <100.00%> (ø)` | | 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=spiral). 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=spiral)

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