manage_delObjects now raises if emtpy list is given as param

bt5/erp5_ui_test_core/SkinTemplateItem/portal_skins/erp5_ui_test_core/TestTool_cleanUpTestResults.py

+from zExceptions import BadRequest
 portal_tests = container.portal_tests
 if test_zuite_relative_url is not None:
   # we care for a specific test zuite
   portal_tests = portal_tests.restrictedTraverse(test_zuite_relative_url,\
                                                  portal_tests)
 # remove test results from previous test runs
-portal_tests.manage_delObjects([x.getId() \
+try:
+  portal_tests.manage_delObjects([x.getId() \
           for x in portal_tests.objectValues('Zuite Results')])
+except BadRequest:
+  pass
 print "OK"
 return printed