Fix index bug in readResults

tools/gardening/lib/src/compare_failures_impl.dart

Index: tools/gardening/lib/src/compare_failures_impl.dart
diff --git a/tools/gardening/lib/src/compare_failures_impl.dart b/tools/gardening/lib/src/compare_failures_impl.dart
index 886d06f1efa84d6882cda50061af6b1457c4aa51..6104fba670f634b52c1e6e94d27d8021301525c0 100644
--- a/tools/gardening/lib/src/compare_failures_impl.dart
+++ b/tools/gardening/lib/src/compare_failures_impl.dart
@@ -37,7 +37,11 @@ Future<Map<BuildUri, List<BuildResult>>> loadBuildResults(
   Map<BuildUri, List<BuildResult>> pastResultsMap =
       <BuildUri, List<BuildResult>>{};
   List<BuildResult> buildResults = await bot.readResults(buildUriList);
-  for (int index = 0; index < buildUriList.length; index++) {
+  if (buildResults.length != buildUriList.length) {
+    print('Result mismatch: Pulled ${buildUriList.length} uris, '
+        'received ${buildResults.length} results.');
+  }
+  for (int index = 0; index < buildResults.length; index++) {
     BuildUri buildUri = buildUriList[index];
     BuildResult buildResult = buildResults[index];
     List<BuildResult> results =