Remove use of C-style casts

src/core/stylehelper.cpp

@@ -369,7 +369,7 @@ QPixmap StyleHelper::disabledSideBarIcon(const QPixmap &enabledicon) {
     auto scanLine = reinterpret_cast<QRgb*>(im.scanLine(y));
     for (int x=0; x<im.width(); ++x) {
       QRgb pixel = *scanLine;
-      char intensity = char(qGray(pixel));
+      char intensity = static_cast<char>(qGray(pixel));
       *scanLine = qRgba(intensity, intensity, intensity, qAlpha(pixel));
       ++scanLine;
     }