erp5_property_sheets: change initial_value_property type to fix converted edit workflow error.

product/ERP5/bootstrap/erp5_property_sheets/PropertySheetTemplateItem/portal_property_sheets/Variable/initial_value_property.xml

@@ -27,7 +27,7 @@
             <key> <string>categories</string> </key>
             <value>
               <tuple>
-                <string>elementary_type/tales</string>
+                <string>elementary_type/string</string>
               </tuple>
             </value>
         </item>
@@ -47,6 +47,12 @@
             <key> <string>portal_type</string> </key>
             <value> <string>Standard Property</string> </value>
         </item>
+        <item>
+            <key> <string>property_default</string> </key>
+            <value>
+              <none/>
+            </value>
+        </item>
         <item>
             <key> <string>storage_id</string> </key>
             <value> <string>default_value</string> </value>