fix(sse): prevent errors by returning early if response data is undefined

packages/plugins/@nocobase/plugin-notification-in-app-message/src/client/observables/sse.ts

@@ -53,6 +53,7 @@ export const startMsgSSEStreamWithRetry: () => () => void = () => {
       responseType: 'stream',
       adapter: 'fetch',
     });
+    if (!res?.data) return;
     const stream = res.data;
     const reader = stream.pipeThrough(new TextDecoderStream()).getReader();
     retryTimes = 0;