Force engine setup.

If we where not in full help mode at least once, the engine
would still run without valid help collection due to the new
lazy initialisation, thus the right side pane would not be
able to retrieve the requested help file.

Reviewed-by: ck

src/plugins/help/helpplugin.cpp

@@ -532,6 +532,10 @@ void HelpPlugin::createRightPaneContextViewer()
     connect(copy, SIGNAL(triggered()), m_helpViewerForSideBar, SLOT(copy()));
     connect(next, SIGNAL(triggered()), m_helpViewerForSideBar, SLOT(forward()));
     connect(previous, SIGNAL(triggered()), m_helpViewerForSideBar, SLOT(backward()));
+
+    // force setup, as we might have never switched to full help mode
+    // thus the help engine might still run without collection file setup
+    m_helpManager->setupGuiHelpEngine();
 }
 
 void HelpPlugin::activateHelpMode()