fix compiler warning on mingw

[mattn]

No description provided.

[codecov]

Codecov Report

Merging #10589 (ac4ec0a) into master (156d391) will decrease coverage by 0.00%.
The diff coverage is n/a.

@@            Coverage Diff             @@
##           master   #10589      +/-   ##
==========================================
- Coverage   81.70%   81.69%   -0.01%     
==========================================
  Files         158      158              
  Lines      185381   185381              
  Branches    41931    41931              
==========================================
- Hits       151463   151453      -10     
- Misses      21464    21470       +6     
- Partials    12454    12458       +4     

Flag	Coverage Δ
huge-clang-none	82.60% <ø> (-0.01%)	⬇️
linux	82.60% <ø> (-0.01%)	⬇️
mingw-x64-HUGE	0.00% <ø> (ø)
mingw-x64-HUGE-gui	78.13% <ø> (-0.01%)	⬇️
windows	76.90% <ø> (-0.01%)	⬇️

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Impacted Files	Coverage Δ
src/os_win32.c	57.42% <ø> (ø)
src/os_mswin.c	48.94% <0.00%> (-1.27%)	⬇️
src/profiler.c	82.48% <0.00%> (-0.67%)	⬇️
src/os_unix.c	67.53% <0.00%> (-0.22%)	⬇️
src/channel.c	83.87% <0.00%> (-0.14%)	⬇️
src/gui.c	73.10% <0.00%> (-0.05%)	⬇️
src/gui_w32.c	34.87% <0.00%> (-0.04%)	⬇️
src/version.c	84.16% <0.00%> (ø)
src/terminal.c	77.09% <0.00%> (+0.05%)	⬆️
... and 5 more

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