fix: 管理删评对公众剥离作者身份，评论者本人仍可见原文

Co-authored-by: Cursor <cursoragent@cursor.com>

frontend/app/post/[id]/page.tsx

@@ -546,10 +546,12 @@ export default async function PostDetailPage({ params, searchParams }: PageProps
           "@type": "Comment",
           text: acceptedAnswer.content,
           dateCreated: acceptedAnswer.created_at,
-          author: {
-            "@type": "Person",
-            name: acceptedAnswer.user.nickname || acceptedAnswer.user.username,
-          },
+          author: acceptedAnswer.user
+            ? {
+                "@type": "Person",
+                name: acceptedAnswer.user.nickname || acceptedAnswer.user.username,
+              }
+            : undefined,
           url: `#comment-${acceptedAnswer.id}`,
         },
       }),