Bug: "No content to display" when using OpenRouter as backend

[x7007x]

Problem

When using OpenRouter as ANTHROPIC_BASE_URL, bot always returns "No content to display".

Root Cause

ResultMessage.result returns '' (empty string) with OpenRouter, not None.

Line 569 in sdk_integration.py:
if result_content is not None: → True for empty string → returns blank content

Fix (one line)

Change line 569 from:
if result_content is not None:

To:
if result_content:

Tested

OpenRouter + qwen/qwen3.6-plus:free ✅