https://github.com/DaveDavenport/gpx-viewer/commit/9cb7021c05c118456ec21790d4a9b2454509c3b4

--- data/gpx-viewer-preferences.ui.orig	Sun Sep 20 11:14:49 2015
+++ data/gpx-viewer-preferences.ui	Sun Sep 20 11:15:00 2015
@@ -5,7 +5,6 @@
   <object class="GtkDialog" id="preferences_dialog">
     <property name="border_width">5</property>
     <property name="type_hint">normal</property>
-    <property name="has_separator">False</property>
     <signal name="response" handler="gpx_viewer_preferences_close"/>
     <child internal-child="vbox">
       <object class="GtkVBox" id="dialog-vbox1">