Issue Summary

Epics are not available in filter on Backlog view if excluded by Board Filter

Steps to Reproduce

1. Create a Kanban board with filter explicitly excluding Epics like 

project in ("Project Name") and issuetype !=Epic ORDER BY Rank ASC 

1. Enable Backlog on Kanban board and map some statuses.
2. Make sure you have work items with parent Epics. Such work items should be present in both backlog and Kanban board statuses.
3. Go to Kanban board and click on "Epic" filter on top and observe Epics are available.
4. Go to Backlog, click on "Epic" filter on top and observe Epics are not available.

Expected Results

Epics are available in filter on Backlog view (the same experience as Kanban board) 

Actual Results

Epics are not available in filter on Backlog view

Workaround

The only workaround is to adjust board filter to include Epics, e.g.

project in ("Project Name") and issuetype !=Epic ORDER BY Rank ASC