Describe top level groups as 'top level' instead of 'no parent'

rhodecode/model/db.py

@@ -1251,7 +1251,7 b' class RepoGroup(Base, BaseModel):'
 
         repo_groups = []
         if show_empty_group:
-            repo_groups = [('-1', '-- no parent --')]
+            repo_groups = [('-1', '-- %s --' % _('top level'))]
         sep = ' » '
         _name = lambda k: _literal(sep.join(k))