Help Window: Add missing connect for contents view action

Change-Id: I4504f00d138e42453132ee7ec7513216ab9e783b
Reviewed-by: Eike Ziller <eike.ziller@theqtcompany.com>

src/plugins/help/helpwidget.cpp

@@ -378,6 +378,9 @@ void HelpWidget::addSideBar()
     m_sideBar->readSettings(Core::ICore::settings(), sideBarSettingsKey());
     m_sideBarSplitter->setSizes(QList<int>() << m_sideBar->size().width() << 300);
 
+    connect(m_contentsAction, &QAction::triggered, m_sideBar, [this]() {
+        m_sideBar->activateItem(QLatin1String(Constants::HELP_CONTENTS));
+    });
     connect(m_indexAction, &QAction::triggered, m_sideBar, [this]() {
         m_sideBar->activateItem(QLatin1String(Constants::HELP_INDEX));
     });