Small improvements to bot summary.

tools/gardening/lib/src/client.dart

Index: tools/gardening/lib/src/client.dart
diff --git a/tools/gardening/lib/src/client.dart b/tools/gardening/lib/src/client.dart
index 2dc28333c75eb1168fd935d2b146f8edb5eccfd2..fb83275e982ebb4bba3f81328a841e4787ba1e71 100644
--- a/tools/gardening/lib/src/client.dart
+++ b/tools/gardening/lib/src/client.dart
@@ -30,7 +30,9 @@ class HttpBuildbotClient implements BuildbotClient {
   Future<BuildResult> readResult(BuildUri buildUri) async {
     try {
       return await readBuildResultFromHttp(_client, buildUri);
-    } on HttpException {
+    } on HttpException catch (e) {
+      return null;
+    } on SocketException catch (e) {
       return null;
     }
   }