Fix potential error message in retrigger job

TypeError: 'NoneType' object is not subscriptable
Example:
https://git.seco.com/seco-ne/yocto/infrastructure/ci-test/minimal-manifest/-/jobs/127610

scripts/retrigger_pipeline_jobs.py

@@ -20,7 +20,10 @@ def retrigger_pipeline_jobs(
     # Recurse to child pipelines
     if include_children:
         for bridge in pipeline.bridges.list():
-            if bridge.downstream_pipeline["project_id"] == project.id:
+            if (
+                bridge is not None
+                and bridge.downstream_pipeline["project_id"] == project.id
+            ):
                 child_pipeline = project.pipelines.get(
                     bridge.downstream_pipeline["id"],
                     retry_transient_errors=True,