Update src/server.ts

src/server.ts

@@ -31,10 +31,12 @@ class IdempotencyCache {
   constructor(maxSize = 2000) { this.maxSize = maxSize; }
   has(uuid: string) { return this.map.has(uuid); }
   add(uuid: string) {
-    this.map.set(uuid, true);
-    if (this.map.size > this.maxSize) {
-      const firstKey = this.map.keys().next().value;
+  this.map.set(uuid, true);
+  if (this.map.size > this.maxSize) {
+    const firstKey = this.map.keys().next().value as string | undefined;
+    if (firstKey !== undefined) {
       this.map.delete(firstKey);
+      }
     }
   }
 }