Add debug log for missing PIS code

Signed-off-by: Fred Boniface <fred@fjla.uk>

src/services/trainService.services.ts

@@ -107,7 +107,9 @@ async function fetchPisCode(
       code: randomEcsPis(),
     };
   }
-
+  if (!pisData) {
+    logger.debug(tiplocList, "No PIS found for service")
+  }
   return pisData;
 }