Unknown sort_on index (undefined)

Yesterday i updated my Plone 4 Installation from 4.3.11 to 4.3.14. Now i get many Tracebacks if a query is send to livesearch_reply in the Searchportlet.

Traceback (innermost last):
  Module ZPublisher.Publish, line 138, in publish
  Module ZPublisher.mapply, line 77, in mapply
  Module ZPublisher.Publish, line 48, in call_object
  Module Shared.DC.Scripts.Bindings, line 322, in __call__
  Module Shared.DC.Scripts.Bindings, line 359, in _bindAndExec
  Module Products.PythonScripts.PythonScript, line 344, in _exec
  Module script, line 176, in livesearch_reply
   - <CustomizedPythonScript at /xxx/xxx/livesearch_reply used for /xxx/xxx/de>
   - Line 176
  Module AccessControl.ZopeGuards, line 369, in guarded_apply
  Module AccessControl.ZopeGuards, line 391, in builtin_guarded_apply
  Module Products.CMFPlone.CatalogTool, line 389, in searchResults
  Module Products.ZCatalog.ZCatalog, line 604, in searchResults
  Module Products.ZCatalog.Catalog, line 916, in searchResults
  Module Products.ZCatalog.Catalog, line 889, in _getSortIndex
CatalogError: Unknown sort_on index (undefined)

Any Hints or Ideas?

Perhaps an index disappeared during the migration? At least you are using a customized search script. Debug the name of the index used for sort_on and then check the portal catalog for the existence of this index.

Ok i found the problem in my Webserver Logfile. Anyone or whatever send this query: