fix: avoid webchat stream result crash on queue errors (#6123)

Co-authored-by: stablegenius49 <185121704+stablegenius49@users.noreply.github.com>

tests/test_chat_route.py

@@ -0,0 +1,56 @@
+import asyncio
+
+import pytest
+
+from astrbot.dashboard.routes.chat import _poll_webchat_stream_result
+
+
+class _QueueThatRaises:
+    def __init__(self, exc: BaseException):
+        self._exc = exc
+
+    async def get(self):
+        raise self._exc
+
+
+class _QueueWithResult:
+    def __init__(self, result):
+        self._result = result
+
+    async def get(self):
+        return self._result
+
+
+@pytest.mark.asyncio
+async def test_poll_webchat_stream_result_breaks_on_cancelled_error():
+    result, should_break = await _poll_webchat_stream_result(
+        _QueueThatRaises(asyncio.CancelledError()),
+        "alice",
+    )
+
+    assert result is None
+    assert should_break is True
+
+
+@pytest.mark.asyncio
+async def test_poll_webchat_stream_result_continues_on_generic_exception():
+    result, should_break = await _poll_webchat_stream_result(
+        _QueueThatRaises(RuntimeError("boom")),
+        "alice",
+    )
+
+    assert result is None
+    assert should_break is False
+
+
+@pytest.mark.asyncio
+async def test_poll_webchat_stream_result_returns_queue_payload():
+    payload = {"type": "end", "data": ""}
+
+    result, should_break = await _poll_webchat_stream_result(
+        _QueueWithResult(payload),
+        "alice",
+    )
+
+    assert result == payload
+    assert should_break is False