Fix unnecessary epics fetch request on Roadmap with no filter token value

What does this MR do and why?

This MR fixes a bug where the roadmap would fetch epics even when no filter token value is selected.

Screenshots or screen recordings

Before	After
Epics getting re-fetched	Epics staying as it is

How to set up and validate locally

Numbered steps to set up and validate the change are strongly suggested.

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