Resolves: tdf#91864 unset a dying childwindow as the active window

Change-Id: Ief014895facbc092913b3069ed04cace1e233ff0
(cherry picked from commit 8f99f936)

sfx2/source/appl/childwin.cxx

@@ -177,7 +177,12 @@ void SfxChildWindow::Destroy()
 {
     if ( GetFrame().is() )
     {
-        pImp->pWorkWin = NULL;
+        if (pImp->pWorkWin)
+        {
+            if (pImp->pWorkWin->GetActiveChild_Impl() == pWindow)
+                pImp->pWorkWin->SetActiveChild_Impl(NULL);
+            pImp->pWorkWin = NULL;
+        }
         try
         {
             ::com::sun::star::uno::Reference < ::com::sun::star::util::XCloseable > xClose( GetFrame(), ::com::sun::star::uno::UNO_QUERY );

sfx2/source/inc/workwin.hxx

@@ -322,6 +322,7 @@ public:
     bool                    IsVisible_Impl( sal_uInt16 nMode ) const;
     bool                    IsFloating( sal_uInt16 nId );
     void                    SetActiveChild_Impl( vcl::Window *pChild );
+    VclPtr<vcl::Window>     GetActiveChild_Impl() const { return pActiveChild; }
     bool                    ActivateNextChild_Impl( bool bForward = true );
     bool                    AllowChildWindowCreation_Impl( const SfxChildWin_Impl& i_rCW ) const;