fix(feishu): tolerate null multi_url and list fields in card extract

nanobot/channels/feishu/tests/test_feishu_card_extraction.py

@@ -1,6 +1,7 @@
 import json
 
 from nanobot.channels.feishu.runtime import (
+    _extract_element_content,
     _extract_post_content,
     _extract_share_card_content,
 )
@@ -60,3 +61,28 @@ def test_extract_post_content_tolerates_null_fields() -> None:
     assert "@user" in text
     assert "ok" in text
     assert images == []
+
+
+def test_extract_button_tolerates_null_multi_url() -> None:
+    element = {"tag": "button", "text": {"content": "Go"}, "multi_url": None}
+    assert _extract_element_content(element) == ["Go"]
+
+
+def test_extract_column_set_tolerates_null_columns_and_elements() -> None:
+    assert _extract_element_content({"tag": "column_set", "columns": None}) == []
+    assert _extract_element_content(
+        {"tag": "column_set", "columns": [{"elements": None}]}
+    ) == []
+
+
+def test_extract_div_tolerates_null_fields() -> None:
+    assert _extract_element_content(
+        {"tag": "div", "text": {"content": "hi"}, "fields": None}
+    ) == ["hi"]
+
+
+def test_interactive_card_button_null_multi_url() -> None:
+    content = {
+        "elements": [{"tag": "button", "text": {"content": "Go"}, "multi_url": None}]
+    }
+    assert _extract_share_card_content(content, "interactive") == "Go"