I used to be able to search all my maintenance periods.   Used to have at the top of the hostgroup list "all", but that's not longer there, but sometimes the hostgroup select filed shows the item "not selected"

Now in order for me to delete a maintenance, I have to guess which host group the maintenance may be assigned to.   

Steps to reproduce:

1. go to configuration -> maintenance
2. all hostgroup is missing, tried using 'not selected' host group
3. Result: no maintenance periods show up**

Expected:
expect to see list of all the maintenance periods