fix typo

Author: Germain Souquet

src/client.ts

@@ -4590,7 +4590,8 @@ export class MatrixClient extends TypedEventEmitter<EmittedEvents, ClientEventHa
             $eventId: event.getId(),
         });
 
-        if (event.threadRootId) {
+        const isThread = !!event.threadRootId;
+        if (isThread) {
             path += utils.encodeUri("/$threadId", {
                 $threadId: event.threadRootId,
             });

src/models/room.ts

@@ -2463,7 +2463,7 @@ export class Room extends TimelineReceipts<EmittedEvents, RoomEventHandlerMap> {
                     // hack, threadId should be thread_id
                     const receipt = content[eventId][receiptType][userId] as any;
 
-                    const receiptDestination = this.threads.get(receipt.threadId) ?? this;
+                    const receiptDestination = this.threads.get(receipt.thread_id) ?? this;
                     receiptDestination.addReceiptToStructure(
                         eventId,
                         receiptType,