Merge pull request #716 from grafana/matiasb/fix-incident-log-no-backend

Fix error when generating log line for non-handled messaging backend

engine/apps/alerts/incident_log_builder/incident_log_builder.py

@@ -596,7 +596,7 @@ class IncidentLogBuilder:
                 except ValueError:
                     pass
                 else:
-                    result += f"send {backend.label.lower()} message to {user_verbal}"
+                    result += f"send {backend.label.lower() if backend else ''} message to {user_verbal}"
         if not result:
             result += f"inviting {user_verbal} but notification channel is unspecified"
         return result