Add optional column on tree view

issue10989
review374321002

view/product_tree.xml

@@ -3,7 +3,7 @@
 this repository contains the full copyright notices and license terms. -->
 <data>
     <xpath expr="//field[@name='name']" position="after">
-        <field name="attributes_name" expand="1"/>
+        <field name="attributes_name" expand="1" optional="1"/>
     </xpath>
     <xpath expr="//field[@name='attribute_set']" position="after">
         <field name="attributes" tree_invisible="1"/>

view/template_tree.xml

@@ -3,6 +3,6 @@
 this repository contains the full copyright notices and license terms. -->
 <data>
     <xpath expr="//field[@name='type']" position="after">
-        <field name="attribute_set"/>
+        <field name="attribute_set" optional="1"/>
     </xpath>
 </data>