Created attachment 1223795 [details]
screenshot

Description of problem:
When I open Policy Timelines f.e. for vm first time, I see appropriate policy events. However, when I change any settings like Interval or Event Type (uncheck and check "Check All"), timeline control disappears from the view.
The only way to get Policy Events rendered correctly again is switching between Management and Policy events. (See screenshot)

Version-Release number of selected component (if applicable):
5.6.3.2

How reproducible:
100%

Steps to Reproduce:
1. Add some provider to appliance (I used vpshere55)
2. Create some Policy Profile + Policy with Conditions and Events (my conditions and events were related to changing VM Power State)
3. find any available vm
4. Assign just created policy profile to this vm
5. Power off and power on this vm
6. check that appropriate policy events showed up in policy_events table
7. Open Timelines for that vm
8. Change Timelines to display policy events
9. try to change Interval or uncheck and check again Event Type->Check All checkbox 

Actual results:
After 8 step, Policy Timelines displays appropriate events.
After 9 step, Timelines control disappears from Timelines view.
Reopening timelines doesn't help. Policy Timelines will be rendered correctly only after switch Management Events.

Expected results:
correct rendering of Policy Timelines when filtering settings are changed.