fix(dot/network): fix justification request at head logic (#1510)

Author: noot

dot/network/sync_justification.go

@@ -36,6 +36,15 @@ func (q *syncQueue) finalizeAtHead() {
 			return
 		}
 
+		head, err := q.s.blockState.BestBlockNumber()
+		if err != nil {
+			continue
+		}
+
+		if head.Int64() < q.goal {
+			continue
+		}
+
 		curr, err := q.s.blockState.GetFinalizedHeader(0, 0)
 		if err != nil {
 			continue
@@ -50,12 +59,6 @@ func (q *syncQueue) finalizeAtHead() {
 
 		prev = curr
 
-		// no new blocks have been finalized, request block justifications from peers
-		head, err := q.s.blockState.BestBlockNumber()
-		if err != nil {
-			continue
-		}
-
 		start := head.Uint64() - uint64(blockRequestSize)
 		if curr.Number.Uint64() > start {
 			start = curr.Number.Uint64() + 1