Issue 7532. Fix for NPE in SemanticHighlightings

compiler/java/com/google/dart/compiler/resolver/LibraryElementImplementation.java

 // Copyright (c) 2012, 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.
 
 package com.google.dart.compiler.resolver;
 
 import com.google.common.collect.Maps;
 import com.google.dart.compiler.ast.DartObsoleteMetadata;
 import com.google.dart.compiler.ast.LibraryUnit;
 
 import java.util.Collection;
 import java.util.Map;
 
 class LibraryElementImplementation extends AbstractNodeElement implements LibraryElement {
 
   private final Scope importScope = new Scope("import", this);
   private final Scope scope = new Scope("library", this, importScope);
   private final Map<String, Element> exportedElements = Maps.newHashMap();
   private LibraryUnit libraryUnit;
   private MethodElement entryPoint;
-  private DartObsoleteMetadata metadata;
+  private DartObsoleteMetadata metadata = DartObsoleteMetadata.EMPTY;
 
   public LibraryElementImplementation(LibraryUnit libraryUnit) {
     // TODO(ngeoffray): What should we pass the super? Should a LibraryUnit be a node?
     super(null, libraryUnit.getSource().getName());
     this.libraryUnit = libraryUnit;
   }
 
   @Override
   public boolean isInterface() {
     return false;
@@ skipping 59 matching lines @@
   
   @Override
   public DartObsoleteMetadata getMetadata() {
     return metadata;
   }
 
   public void setMetadata(DartObsoleteMetadata metadata) {
     this.metadata = metadata;
   }
 }