fix: handle empty content in tool result parsing

Author: liuruibin

apps/application/flow/tools.py

@@ -399,14 +399,18 @@ async def _yield_mcp_response(chat_model, message_list, mcp_servers, mcp_output_
 
                 if tool_id in tool_calls_info:
                     tool_info = tool_calls_info[tool_id]
-                    tool_result = json.loads(chunk[0].content)
-                    tool_lib_id = tool_result.pop('tool_id') if 'tool_id' in tool_result else None
-                    if tool_lib_id:
-                        await save_tool_record(tool_lib_id, tool_info, tool_result, source_id, source_type)
+                    try:
+                        tool_result = json.loads(chunk[0].content)
+                        tool_lib_id = tool_result.pop('tool_id') if 'tool_id' in tool_result else None
+                        if tool_lib_id:
+                            await save_tool_record(tool_lib_id, tool_info, tool_result, source_id, source_type)
+                        tool_result = json.dumps(tool_result)
+                    except Exception as e:
+                        tool_result = chunk[0].content
                     content = generate_tool_message_complete(
                         tool_info['name'],
                         tool_info['input'],
-                        json.dumps(tool_result),
+                        tool_result
                     )
                     chunk[0].content = content
                 else: