UI: Fix compile issue

UI/adv-audio-control.cpp

@@ -4,6 +4,7 @@
 #include <QSpinBox>
 #include <QComboBox>
 #include <QCheckBox>
+#include <cmath>
 #include "qt-wrappers.hpp"
 #include "obs-app.hpp"
 #include "adv-audio-control.hpp"