Fix for wxUniv/GTK compilation.

wxWindowBase needs to be explicitly cast to wxWindow in wxUniv/GTK build but
this wasn't done in the changes of r70597.

Cloes #14235.

git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/trunk@71235 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775

src/gtk/window.cpp

@@ -1166,7 +1166,7 @@ wxWindowGTK *FindWindowForMouseEvent(wxWindowGTK *win, wxCoord& x, wxCoord& y)
     wxWindowList::compatibility_iterator node = win->GetChildren().GetFirst();
     while (node)
     {
-        wxWindowGTK *child = node->GetData();
+        wxWindow* child = static_cast<wxWindow*>(node->GetData());
 
         node = node->GetNext();
         if (!child->IsShown())