fix(async search): skip missing fracs

[forshev]

Description

Skip evicted fracs in async search

---

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[github-actions]

🔴 Performance Degradation

Some benchmarks have degraded compared to the previous run.
Click on Show table button to see full list of degraded benchmarks.

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Name	Previous	Current	Ratio	Verdict
GenerateDocs-4	6ae568	044fcb
	957.90 ns/op	1132.00 ns/op	1.18	🔴
MutexListAppend-4	6ae568	044fcb
	184.44 MB/s	166.21 MB/s	0.90	🔴

[codecov-commenter]

Codecov Report

❌ Patch coverage is 25.00000% with 3 lines in your changes missing coverage. Please review.
✅ Project coverage is 71.46%. Comparing base (1d2edc4) to head (19219ab).

Files with missing lines	Patch %	Lines
asyncsearcher/async_searcher.go	25.00%	2 Missing and 1 partial ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #343      +/-   ##
==========================================
- Coverage   71.55%   71.46%   -0.09%     
==========================================
  Files         204      204              
  Lines       14928    14931       +3     
==========================================
- Hits        10681    10671      -10     
- Misses       3480     3489       +9     
- Partials      767      771       +4     

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[github-actions]

🔴 Performance Degradation

Some benchmarks have degraded compared to the previous run.
Click on Show table button to see full list of degraded benchmarks.

Show table

Name	Previous	Current	Ratio	Verdict
Bitmask-4	b9c2c0	7046c4
	0.00 B/op	3.00 B/op	NaN	🔴
GenerateDocs-4	b9c2c0	7046c4
	935.60 ns/op	1143.00 ns/op	1.22	🔴

[github-actions]

🔴 Performance Degradation

Some benchmarks have degraded compared to the previous run.
Click on Show table button to see full list of degraded benchmarks.

Show table

Name	Previous	Current	Ratio	Verdict
FindSequence_Random/large-4	1d2edc	1b8dd4
	13163.26 MB/s	11341.66 MB/s	0.86	🔴
	1245.00 ns/op	1445.00 ns/op	1.16	🔴
FindSequence_Random/medium-4	1d2edc	1b8dd4
	11008.63 MB/s	7497.74 MB/s	0.68	🔴
	93.02 ns/op	136.60 ns/op	1.47	🔴
GenerateDocs-4	1d2edc	1b8dd4
	948.80 ns/op	1127.00 ns/op	1.19	🔴