fix(net):optimize getBlockIdByNum in SyncService

Author: 317787106

framework/src/main/java/org/tron/core/net/service/sync/SyncService.java

@@ -209,11 +209,12 @@ private LinkedList<BlockId> getBlockChainSummary(PeerConnection peer) throws P2p
   }
 
   private BlockId getBlockIdByNum(long num) throws P2pException {
-    BlockId head = tronNetDelegate.getHeadBlockId();
-    if (num > head.getNum()) {
-      return tronNetDelegate.getKhaosDbHeadBlockId();
-    } else if (num == head.getNum()) {
-      return head;
+    BlockId head1 = tronNetDelegate.getKhaosDbHeadBlockId();
+    BlockId head2 = tronNetDelegate.getHeadBlockId();
+    if (num == head1.getNum()) {
+      return head1;
+    } else if (num == head2.getNum()) {
+      return head2;
     }
     return tronNetDelegate.getBlockIdByNum(num);
   }