eth/downloader: fix ancestor searching for light syncing (#19136)

eth/downloader/downloader.go

@@ -665,10 +665,12 @@ func (d *Downloader) findAncestor(p *peerConnection, remoteHeader *types.Header)
 		localHeight = d.lightchain.CurrentHeader().Number.Uint64()
 	}
 	p.log.Debug("Looking for common ancestor", "local", localHeight, "remote", remoteHeight)
+
+	// Recap floor value for binary search
 	if localHeight >= MaxForkAncestry {
 		// We're above the max reorg threshold, find the earliest fork point
 		floor = int64(localHeight - MaxForkAncestry)
-
+	}
 	// If we're doing a light sync, ensure the floor doesn't go below the CHT, as
 	// all headers before that point will be missing.
 	if d.mode == LightSync {
@@ -688,7 +690,7 @@ func (d *Downloader) findAncestor(p *peerConnection, remoteHeader *types.Header)
 			floor = int64(d.genesis) - 1
 		}
 	}
-	}
+
 	from, count, skip, max := calculateRequestSpan(remoteHeight, localHeight)
 
 	p.log.Trace("Span searching for common ancestor", "count", count, "from", from, "skip", skip)