support anthropic endpoint

Signed-off-by: liuli <[email protected]>

Author: Liliu1997

vllm/entrypoints/anthropic/serving_messages.py

@@ -324,6 +324,8 @@ async def message_stream_converter(
                                 yield f"data: {data}\n\n"
                                 content_block_started = True
 
+                            if origin_chunk.choices[0].delta.content == "":
+                                continue
                             chunk = AnthropicStreamEvent(
                                 index=content_block_index,
                                 type="content_block_delta",