suppress warning about unused win pointer when wxUSE_GRAPHICS_CONTEXT==0

git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/trunk@58436 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775

src/gtk/renderer.cpp

@@ -157,6 +157,11 @@ static GdkWindow* wxGetGdkWindowForDC(wxWindow* win, wxDC& dc)
         gdk_window = dc.GetGDKWindow();
 #endif
     }
+
+#if !wxUSE_GRAPHICS_CONTEXT
+    wxUnusedVar(win);
+#endif
+
     return gdk_window;
 }