Merge pull request #471 from guagualvcha/down_nil_issue

[R4R]fix downloader nil issue when the header is mising

eth/downloader/downloader.go

@@ -1028,8 +1028,8 @@ func (d *Downloader) findAncestorBinarySearch(p *peerConnection, mode SyncMode,
 				}
 				header := d.lightchain.GetHeaderByHash(h) // Independent of sync mode, header surely exists
 				if header == nil {
-					p.log.Error("header not found", "number", header.Number, "hash", header.Hash(), "request", check)
-					return 0, fmt.Errorf("%w: header no found (%d)", errBadPeer, header.Number)
+					p.log.Error("header not found", "hash", h, "request", check)
+					return 0, fmt.Errorf("%w: header no found (%s)", errBadPeer, h)
 				}
 				if header.Number.Uint64() != check {
 					p.log.Warn("Received non requested header", "number", header.Number, "hash", header.Hash(), "request", check)