The presence of the featured slider depends on what you select for header style.
Highlight, Magazine: slider is present
Landing, Search, Off: slider is NOT present
That’s why I am surprised to see an empty Featured section with header style set to Search.
Interesting: I set header style to Off. Saved. Set header style back to Search. Saved. And (for now) the empty Featured section is gone.
Seems like a bug, so I filed this report: Empty Featured section with Source theme and Search header style