Fix build with -no-feature-menu

Change-Id: I29a230d70a96c3037f4e07dbe23fce13aa869089
Reviewed-by: Richard Moe Gustavsen <richard.gustavsen@qt.io>

src/widgets/dialogs/qsidebar.cpp

@@ -364,9 +364,11 @@ void QSidebar::setModelAndUrls(QFileSystemModel *model, const QList<QUrl> &newUr
 #if QT_CONFIG(draganddrop)
     setDragDropMode(QAbstractItemView::DragDrop);
 #endif
+#if QT_CONFIG(menu)
     setContextMenuPolicy(Qt::CustomContextMenu);
     connect(this, &QSidebar::customContextMenuRequested,
             this, &QSidebar::showContextMenu);
+#endif
     urlModel->setUrls(newUrls);
     setCurrentIndex(this->model()->index(0,0));
 }