Add const and std::as_const

src/core/stylehelper.cpp

@@ -176,7 +176,8 @@ void StyleHelper::setBaseColor(const QColor &newcolor) {
 
   if (color.isValid() && color != m_baseColor) {
     m_baseColor = color;
-    for (QWidget *w : QApplication::topLevelWidgets()) {
+    const QList<QWidget*> widgets = QApplication::topLevelWidgets();
+    for (QWidget *w : widgets) {
       w->update();
     }
   }