[ 1522988 ] Keypress causes crash in combo sample

git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/trunk@40156 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775

samples/combo/combo.cpp

@@ -557,6 +557,11 @@ public:
         }
     }
 
+    // Implement empty DoSetPopupControl to prevent assertion failure.
+    virtual void DoSetPopupControl(wxComboPopup* WXUNUSED(popup))
+    {
+    }
+
 private:
     void Init()
     {