fix: doesnt hang up on call hangup

prisma/schema.prisma

@@ -39,7 +39,7 @@ model Message {
 
   createdAt DateTime @default(now())
   role Role
-  content String
+  content String @default("")
 
   session Session @relation(fields: [sessionId], references: [id])
   sessionId String @db.ObjectId

src/chat.js

@@ -36,7 +36,10 @@ export const chat = async (callId) => {
   for (let msg of msgs) {
     messages.push({
       role: convertRole(msg.role),
-      content: msg.content,
+      content:
+        msg.content.length > 0
+          ? msg.content
+          : "This message was not recorded correctly.",
     });
   }