fix: read cookie if auth header is undefined

[nogic1008]

This PR fixes middleware error on swa-cli

[codecov]

Codecov Report

Attention: Patch coverage is 57.14286% with 6 lines in your changes are missing coverage. Please review.

Project coverage is 96.78%. Comparing base (f351f48) to head (e3358a6).

Files	Patch %	Lines
...es/nuxt-swa/src/runtime/composables/useEasyAuth.ts	25.00%	6 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main      #79      +/-   ##
==========================================
- Coverage   97.73%   96.78%   -0.96%     
==========================================
  Files           8        8              
  Lines         398      404       +6     
  Branches       33       33              
==========================================
+ Hits          389      391       +2     
- Misses          9       13       +4     

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