Added backgorund for tabs

ubl-settings-video.glade

@@ -1,5 +1,5 @@
 <?xml version="1.0" encoding="UTF-8"?>
-<!-- Generated with glade 3.38.2 -->
+<!-- Generated with glade 3.40.0 -->
 <interface domain="ubl-settings-video">
   <requires lib="gtk+" version="3.24"/>
   <requires lib="vte-2.91" version="0.76"/>
@@ -1623,6 +1623,9 @@
                 <property name="tab-fill">False</property>
               </packing>
             </child>
+            <style>
+              <class name="workingbg"/>
+            </style>
           </object>
           <packing>
             <property name="index">-1</property>