fix header bar under linux

[lidaobing]

No description provided.

[codecov]

Codecov Report

❗ No coverage uploaded for pull request base (master@49d83cc). Click here to learn what that means.
The diff coverage is 92.59%.

@@            Coverage Diff            @@
##             master     #454   +/-   ##
=========================================
  Coverage          ?   44.37%           
=========================================
  Files             ?       70           
  Lines             ?     7813           
  Branches          ?        0           
=========================================
  Hits              ?     3467           
  Misses            ?     4346           
  Partials          ?        0           

Impacted Files	Coverage Δ
src/iptux/MainWindow.cpp	26.80% <87.50%> (ø)
src/iptux/AboutDialog.cpp	54.83% <100.00%> (ø)
src/iptux/Application.cpp	45.05% <100.00%> (ø)
src/iptux/DetectPal.cpp	30.55% <100.00%> (ø)

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