Prevent headers already sent error

server/core/controllers/activitypub/utils.ts

@@ -1,12 +1,11 @@
 import express from 'express'
 
-async function activityPubResponse (promise: Promise<any>, res: express.Response) {
+export async function activityPubResponse (promise: Promise<any>, res: express.Response) {
   const data = await promise
 
-  return res.type('application/activity+json; charset=utf-8')
-            .json(data)
-}
+  if (!res.headersSent) {
+    res.type('application/activity+json; charset=utf-8')
+  }
 
-export {
-  activityPubResponse
+  return res.json(data)
 }