fix curl multi bug

[matyhtf]

No description provided.

[codecov]

Codecov Report

Merging #4147 (8e0bb1d) into master (653f2fe) will decrease coverage by 0.01%.
The diff coverage is n/a.

@@            Coverage Diff             @@
##           master    #4147      +/-   ##
==========================================
- Coverage   48.79%   48.78%   -0.02%     
==========================================
  Files          71       71              
  Lines       14281    14281              
==========================================
- Hits         6969     6967       -2     
- Misses       7312     7314       +2     

Impacted Files	Coverage Δ
src/os/async_thread.cc	68.85% <0.00%> (-0.88%)	⬇️
src/protocol/base.cc	63.15% <0.00%> (ø)

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