Fix the missing call to register the qml and internal help files.

src/plugins/help/helpplugin.cpp

@@ -329,6 +329,7 @@ void HelpPlugin::extensionsInitialized()
     // we might need to register creators inbuild help
     filesToRegister.append(QDir::cleanPath(appPath
         + QLatin1String(DOCPATH "qtcreator.qch")));
+    helpManager->registerDocumentation(filesToRegister);
 }
 
 void HelpPlugin::aboutToShutdown()