Change the required gtk to 3.10 in the glade file
<?xml version="1.0" encoding="UTF-8"?>
<!-- Generated with glade 3.20.0 -->
<interface>
- <requires lib="gtk+" version="3.20"/>
+ <requires lib="gtk+" version="3.10"/>
<object class="GtkImage" id="new_tab_image">
<property name="visible">True</property>
<property name="can_focus">False</property>
