Handle diagnostic messages from analyzer that lack a URI.

pkg/testing/lib/src/analyze.dart

 // Copyright (c) 2016, the Dart project authors. Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE.md file.
 
 library testing.analyze;
 
 import 'dart:async' show Stream, Future;
 
 import 'dart:convert' show LineSplitter, UTF8;
 
@@ skipping 148 matching lines @@
   process.stdin.close();
   Future stdoutFuture = parseAnalyzerOutput(process.stdout).toList();
   Future stderrFuture = parseAnalyzerOutput(process.stderr).toList();
   await process.exitCode;
   List<AnalyzerDiagnostic> diagnostics = <AnalyzerDiagnostic>[];
   diagnostics.addAll(await stdoutFuture);
   diagnostics.addAll(await stderrFuture);
   bool hasOutput = false;
   Set<String> seen = new Set<String>();
   for (AnalyzerDiagnostic diagnostic in diagnostics) {
-    String path = diagnostic.uri.path;
+    String path = diagnostic.uri?.path ?? "<unknown>";
     if (exclude.any((RegExp r) => path.contains(r))) continue;
     String message = "$diagnostic";
     if (seen.add(message)) {
       hasOutput = true;
       print(message);
     }
   }
   if (hasOutput) {
     throw "Non-empty output from analyzer.";
   }
   sw.stop();
   print("Running analyzer took: ${sw.elapsed}.");
 }