fix build error caused by wrong ts-strict improvements (#2783)

Co-authored-by: Michael Telatynski <[email protected]>

Author: justjanne

src/crypto/DeviceList.ts

@@ -83,7 +83,7 @@ export class DeviceList extends TypedEventEmitter<EmittedEvents, CryptoEventHand
     // moment represented by the snapshot in the db.
     private syncToken: string | null = null;
 
-    private keyDownloadsInProgressByUser = new Map<string, Promise<void>>;
+    private keyDownloadsInProgressByUser = new Map<string, Promise<void>>();
 
     // Set whenever changes are made other than setting the sync token
     private dirty = false;