Help: call setupData after setting the collection fileData

Setting the collection file leaves the help engine in an invalid state.
It is important to invoke setupData() in order to setup the help engine
again.

Change-Id: I252d7999c113db4f584bcaf94d42c609f507c1cb
Reviewed-by: Eike Ziller <eike.ziller@qt.io>

src/plugins/help/localhelpmanager.cpp

@@ -287,6 +287,7 @@ void LocalHelpManager::setupGuiHelpEngine()
     if (m_needsCollectionFile) {
         m_needsCollectionFile = false;
         helpEngine().setCollectionFile(Core::HelpManager::collectionFilePath());
+        m_guiNeedsSetup = true;
     }
 
     if (m_guiNeedsSetup) {