test(feishu): cover null post metadata fields

nanobot/channels/feishu/tests/test_feishu_card_extraction.py

@@ -42,19 +42,21 @@ def test_extract_interactive_card_reads_table_rows() -> None:
     assert _extract_share_card_content(content, "interactive") == "Name | Score\nAlice | 98"
 
 
-def test_extract_post_content_tolerates_null_text_fields() -> None:
+def test_extract_post_content_tolerates_null_fields() -> None:
     text, images = _extract_post_content(
         {
-            "title": "T",
+            "title": None,
             "content": [
                 [
                     {"tag": "text", "text": None},
                     {"tag": "a", "text": None},
+                    {"tag": "at", "user_name": None},
                     {"tag": "text", "text": "ok"},
                     {"tag": "code_block", "language": None, "text": None},
                 ]
             ],
         }
     )
+    assert "@user" in text
     assert "ok" in text
     assert images == []