test(auditlog): assert ExecutionId threading hops; defensive Guid parse on S&F read

src/ScadaLink.StoreAndForward/StoreAndForwardStorage.cs

@@ -497,10 +497,31 @@ public class StoreAndForwardStorage
                 // Audit Log #23 (ExecutionId Task 4): rows persisted before the
                 // additive migration have no execution_id / source_script value;
                 // IsDBNull guards keep those reading back as null (back-compat).
-                ExecutionId = reader.IsDBNull(12) ? null : Guid.Parse(reader.GetString(12)),
+                // Guid.TryParse (not Parse) guards the retry sweep: a corrupt
+                // non-null execution_id is treated as "no execution id" rather
+                // than throwing FormatException and aborting the whole sweep.
+                ExecutionId = ParseExecutionId(reader, 12),
                 SourceScript = reader.IsDBNull(13) ? null : reader.GetString(13)
             });
         }
         return results;
     }
+
+    /// <summary>
+    /// Audit Log #23 (ExecutionId Task 4): defensively reads the
+    /// <c>execution_id</c> column. A <c>null</c> value (legacy pre-migration
+    /// rows) and a malformed non-null value both yield <c>null</c> — a corrupt
+    /// id must not throw and abort the retry sweep, which reads many rows.
+    /// </summary>
+    private static Guid? ParseExecutionId(System.Data.Common.DbDataReader reader, int ordinal)
+    {
+        if (reader.IsDBNull(ordinal))
+        {
+            return null;
+        }
+
+        return Guid.TryParse(reader.GetString(ordinal), out var executionId)
+            ? executionId
+            : null;
+    }
 }