fix: detect Gitea issues with null pull request metadata

tests/test_gitea_service.py

@@ -89,6 +89,36 @@ def test_sync_and_scan_with_mocked_gitea(db, tmp_path):
     assert len(task_ids) == 1
 
 
+def test_list_open_issues_keeps_normal_issues_with_null_pull_request():
+    def handler(request: httpx.Request) -> httpx.Response:
+        assert request.url.path == "/api/v1/repos/acme/service/issues"
+        return httpx.Response(
+            200,
+            json=[
+                {
+                    "number": 1,
+                    "title": "Normal issue",
+                    "body": "Body",
+                    "state": "open",
+                    "labels": [{"name": "agent:ready"}],
+                    "pull_request": None,
+                },
+                {
+                    "number": 2,
+                    "title": "PR issue",
+                    "body": "Body",
+                    "state": "open",
+                    "labels": [{"name": "agent:ready"}],
+                    "pull_request": {"url": "https://gitea.test/pr/2"},
+                },
+            ],
+        )
+
+    issues = make_client(handler).list_open_issues("acme", "service")
+
+    assert [issue.number for issue in issues] == [1]
+
+
 class FakeWorkspaceManager:
     def __init__(self, root: Path, *, diff: bool = True):
         self.root = root