Fix for NPE when convert error without source.

pkg/analyzer_experimental/lib/analyzer.dart

Index: pkg/analyzer_experimental/lib/analyzer.dart
diff --git a/pkg/analyzer_experimental/lib/analyzer.dart b/pkg/analyzer_experimental/lib/analyzer.dart
index 2a9d9ac46ce19505aaf326d9d3dc0de9156d4a44..cbe76e3ae9da9f1f0ab1a992b0977b2638497ee7 100644
--- a/pkg/analyzer_experimental/lib/analyzer.dart
+++ b/pkg/analyzer_experimental/lib/analyzer.dart
@@ -26,7 +26,13 @@ CompilationUnit parseDartFile(String path) {
   var contents = new File(path).readAsStringSync();
   var errorCollector = new _ErrorCollector();
   var sourceFactory = new SourceFactory.con2([new FileUriResolver()]);
-  var source = sourceFactory.forUri(pathos.toUri(path).toString());
+
+  var absolutePath = pathos.absolute(path);
+  var source = sourceFactory.forUri(pathos.toUri(absolutePath).toString());
+  if (source == null) {

[Brian Wilkerson, 2013/07/30 14:03:01]

We might also want to check whether the source exists.

+    throw new ArgumentError("Can't get source for path $path");
+  }
+
   var scanner = new StringScanner(source, contents, errorCollector);
   var token = scanner.tokenize();
   var parser = new Parser(source, errorCollector);