reuse existing wxGetTopLevelParent() function in wxMessageDialog ctor instead of reimplementing it (yes, it is just 4 lines, but this still was enough for a fatal bug to slip in them...)

git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/trunk@26282 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775

src/gtk/msgdlg.cpp

@@ -39,14 +39,7 @@ wxMessageDialog::wxMessageDialog(wxWindow *parent,
     m_caption = caption;
     m_message = message;
     m_dialogStyle = style;
-
-    if (parent)
-    {    
-        while (!parent->IsTopLevel())
-            parent = parent->GetParent();
-    }
-        
-    m_parent = parent;
+    m_parent = wxGetTopLevelParent(parent);
 }
 
 int wxMessageDialog::ShowModal()