Update src/google/adk/models/anthropic_llm.py

Co-authored-by: gemini-code-assist[bot] <176961590+gemini-code-assist[bot]@users.noreply.github.com>

Author: QuentinFuxa

src/google/adk/models/anthropic_llm.py

@@ -101,7 +101,7 @@ def part_to_message_block(
     response_data = part.function_response.response
 
     # Handle content array format
-    if "content" in response_data and isinstance(response_data["content"], list):
+    if isinstance(response_data, dict) and "content" in response_data and isinstance(response_data["content"], list):
       content_items = []
       for item in response_data["content"]:
         if isinstance(item, dict):