fix dangling download

frontend/src/utils.ts

@@ -26,4 +26,13 @@ export function detectSpeed(str: string): number {
         default:
             return 0
     }
-}
+}
+
+export const updateInStateMap = (k: number, v: any, target: Map<number, any>, callback: Function, remove: boolean = false) => {
+    if (remove) {
+        target.delete(k)
+        callback(new Map(target))
+        return;
+    }
+    callback(new Map(target.set(k, v)));
+}