Fix #450

[codecov-commenter]

Codecov Report

Attention: 1 lines in your changes are missing coverage. Please review.

Comparison is base (1a4ca42) 97.51% compared to head (d6edd93) 97.48%.

Files	Patch %	Lines
blacksheep/server/cors.py	50.00%	1 Missing :warning:

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Additional details and impacted files

```diff @@ Coverage Diff @@ ## main #451 +/- ## ========================================== - Coverage 97.51% 97.48% -0.04% ========================================== Files 67 67 Lines 6353 6355 +2 ========================================== Hits 6195 6195 - Misses 158 160 +2 ```

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