stage_headers: fix uint underflow at parent request (erigontech#10618) (

#482)

Co-authored-by: Alex Sharov <[email protected]>

turbo/stages/headerdownload/header_algos.go

@@ -383,6 +383,9 @@ func (hd *HeaderDownload) RequestMoreHeaders(currentTime time.Time) (*HeaderRequ
 	var penalties []PenaltyItem
 	var req *HeaderRequest
 	hd.anchorTree.Ascend(func(anchor *Anchor) bool {
+		if anchor.blockHeight == 0 { //has no parent
+			return true
+		}
 		if anchor.nextRetryTime.After(currentTime) {
 			// We are not ready to retry this anchor yet
 			dataflow.HeaderDownloadStates.AddChange(anchor.blockHeight-1, dataflow.HeaderRetryNotReady)