Empty block fix.

backend/mempool-config.sample.json

@@ -7,7 +7,7 @@
   "DB_DATABASE": "mempool",
   "API_ENDPOINT": "/api/v1/",
   "ELECTRS_POLL_RATE_MS": 2000,
-  "MEMPOOL_REFRESH_RATE_MS": 10000,
+  "MEMPOOL_REFRESH_RATE_MS": 2000,
   "DEFAULT_PROJECTED_BLOCKS_AMOUNT": 3,
   "KEEP_BLOCK_AMOUNT": 24,
   "INITIAL_BLOCK_AMOUNT": 8,

backend/src/api/blocks.ts

@@ -63,8 +63,8 @@ class Blocks {
         console.log(`${found} of ${txIds.length} found in mempool. ${notFound} not found.`);
 
         transactions.sort((a, b) => b.feePerVsize - a.feePerVsize);
-        block.medianFee = this.median(transactions.map((tx) => tx.feePerVsize));
-        block.feeRange = this.getFeesInRange(transactions, 8);
+        block.medianFee = transactions.length ? this.median(transactions.map((tx) => tx.feePerVsize)) : 0;
+        block.feeRange = transactions.length ? this.getFeesInRange(transactions, 8) : [];
 
         this.blocks.push(block);
         if (this.blocks.length > config.KEEP_BLOCK_AMOUNT) {