do not display preferred value when no value is set

bt5/erp5_crm/SkinTemplateItem/portal_skins/erp5_crm/SystemPreference_viewCustomerRelation/my_preferred_event_assessment_form_id_list.xml

@@ -134,9 +134,7 @@
                 </item>
                 <item>
                     <key> <string>default</string> </key>
-                    <value>
-                      <persistent> <string encoding="base64">AAAAAAAAAAI=</string> </persistent>
-                    </value>
+                    <value> <string></string> </value>
                 </item>
                 <item>
                     <key> <string>description</string> </key>
@@ -297,20 +295,4 @@
       </dictionary>
     </pickle>
   </record>
-  <record id="2" aka="AAAAAAAAAAI=">
-    <pickle>
-      <tuple>
-        <global name="TALESMethod" module="Products.Formulator.TALESField"/>
-        <tuple/>
-      </tuple>
-    </pickle>
-    <pickle>
-      <dictionary>
-        <item>
-            <key> <string>_text</string> </key>
-            <value> <string>python: here.getPreferredEventAssessmentFormIdList() or preferences.getPreferredEventAssessmentFormIdList()</string> </value>
-        </item>
-      </dictionary>
-    </pickle>
-  </record>
 </ZopeData>

bt5/erp5_crm/bt/revision

-630
\ No newline at end of file
+631
\ No newline at end of file