From b5c20734141cd9825b4b082e63cd125cd507b563 Mon Sep 17 00:00:00 2001
From: Mononaut <github@monospace.live>
Date: Thu, 16 Mar 2023 22:15:20 +0900
Subject: [PATCH] Fix getSimilarity error on empty mempool

---
 backend/src/api/websocket-handler.ts | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/backend/src/api/websocket-handler.ts b/backend/src/api/websocket-handler.ts
index 07aac0790..c89179ce7 100644
--- a/backend/src/api/websocket-handler.ts
+++ b/backend/src/api/websocket-handler.ts
@@ -469,7 +469,9 @@ class WebsocketHandler {
       }
     } else if (block.extras) {
       const mBlocks = mempoolBlocks.getMempoolBlocksWithTransactions();
-      block.extras.similarity = Common.getSimilarity(mBlocks[0], transactions);
+      if (mBlocks?.length && mBlocks[0].transactions) {
+        block.extras.similarity = Common.getSimilarity(mBlocks[0], transactions);
+      }
     }
 
     const removed: string[] = [];