base: Person_createUserPreference must now return the created preference

This changes API on a script that some projects have customized, but
getActiveUserPreferecnce "should work" even with an old script not
returning preferences.

In that case, first call to getActiveUserPreference will create
preference but not return it, but next time getActiveUserPreference is
called, the preference will probably be indexed and will be returned.

bt5/erp5_base/SkinTemplateItem/portal_skins/erp5_base/Person_createUserPreference.py

@@ -23,3 +23,5 @@ for assignment in context.contentValues(portal_type='Assignment'):
   if group:
     preference.setPreferredSectionCategory(group)
     preference.setPreferredAccountingTransactionSectionCategory(group)
+
+return preference

bt5/erp5_web_ung_theme/SkinTemplateItem/portal_skins/erp5_web_ung_theme/Person_createUserPreference.py

@@ -24,3 +24,5 @@ for assignment in context.contentValues(portal_type='Assignment'):
   if group:
     preference.setPreferredSectionCategory(group)
     preference.setPreferredAccountingTransactionSectionCategory(group)
+
+return preference