Help: Fix check if help viewer currently has focus.

Fixes a little issue that after opening context help, clicking into the
context help viewer, and pressing F1, the help viewer would show "No
documentation available" instead of opening help mode.

Change-Id: I071c92946214680e82b1f2982b62cc909a272ad5
Reviewed-by: Eike Ziller <eike.ziller@digia.com>

src/plugins/help/helpplugin.cpp

@@ -875,7 +875,8 @@ void HelpPlugin::activateContext()
     createRightPaneContextViewer();
 
     RightPanePlaceHolder *placeHolder = RightPanePlaceHolder::current();
-    if (placeHolder && m_helpViewerForSideBar->hasFocus()) {
+    if (placeHolder && qApp->focusWidget()
+            && qApp->focusWidget() == m_helpViewerForSideBar->focusWidget()) {
         switchToHelpMode();
         return;
     }