tdf#91227 vcl: fix crash in ImplListBox during paste special in Writer

Change-Id: I65637e7a205c443ff104a1ed5469aabd69571635

vcl/source/control/ilstbox.cxx

@@ -2241,6 +2241,9 @@ void ImplListBox::SetNoSelection()
 
 void ImplListBox::GetFocus()
 {
+    if (!maLBWindow || maLBWindow->IsDisposed())
+        return;
+
     maLBWindow->GrabFocus();
 }