Bail early in API analysis if no project is set.

lib/src/rules/package_api_docs.dart

 // Copyright (c) 2015, 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 linter.src.rules.package_api_docs;
 
 import 'package:analyzer/src/generated/ast.dart';
 import 'package:linter/src/ast.dart';
 import 'package:linter/src/linter.dart';
 import 'package:linter/src/project.dart';
@@ skipping 70 matching lines @@
   }
 }
 
 class Visitor extends GeneralizingAstVisitor {
   PackageApiDocs rule;
   Visitor(this.rule);
 
   DartProject get project => rule.project;
 
   void check(Declaration node) {
+    // If no project info is set, bail early.
+    // https://github.com/dart-lang/linter/issues/154
+    if (project == null) {
+      return;
+    }
     if (project.isApi(node.element)) {
       if (node.documentationComment == null) {
         rule.reportLint(getNodeToAnnotate(node));
       }
     }
   }
 
   ///  classMember ::=
   ///    [ConstructorDeclaration]
   ///  | [FieldDeclaration]
@@ skipping 13 matching lines @@
   @override
   visitCompilationUnitMember(CompilationUnitMember node) {
     check(node);
   }
 
   @override
   visitNode(AstNode node) {
     // Don't visit children
   }
 }