Fix introduced bug

pkg/analyzer/lib/src/analyzer_impl.dart

 // Copyright (c) 2013, 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 file.
 
 library analyzer_impl;
 
 import 'dart:async';
 import 'dart:collection';
 import 'dart:io';
 
@@ skipping 134 matching lines @@
   }
 
   Source computeLibrarySource() {
     JavaFile sourceFile = new JavaFile(sourcePath);
     Source source = sdk.fromFileUri(sourceFile.toURI());
     if (source != null) {
       return source;
     }
     source = new FileBasedSource.con2(sourceFile.toURI(), sourceFile);
     Uri uri = context.sourceFactory.restoreUri(source);
+    if (uri == null) {
+      return source;
+    }
     return new FileBasedSource.con2(uri, sourceFile);
   }
 
   /**
    * Create and return the source factory to be used by the analysis context.
    */
   SourceFactory createSourceFactory() {
     List<UriResolver> resolvers = [
       new CustomUriResolver(options.customUrlMappings),
       new DartUriResolver(sdk)
@@ skipping 289 matching lines @@
     }
   }
 
   @override
   void logInformation2(String message, Object exception) {
     if (log) {
       stdout.writeln(message);
     }
   }
 }