Avoid a crash during summary linking when there are inheritance errors.

pkg/analyzer/lib/src/summary/link.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 file.
 
 /**
  * This library is capable of producing linked summaries from unlinked
  * ones (or prelinked ones).  It functions by building a miniature
  * element model to represent the contents of the summaries, and then
  * scanning the element model to gather linked information and adding
  * it to the summary data structures.
@@ skipping 3511 matching lines @@
 
   LibraryElementInBuildUnit(Linker linker, Uri absoluteUri, this._linkedLibrary)
       : super(linker, absoluteUri) {
     _libraryNode = new LibraryNode(this);
   }
 
   /**
    * Get the inheritance manager for this library (creating it if necessary).
    */
   InheritanceManager get inheritanceManager =>
-      _inheritanceManager ??= new InheritanceManager(this);
+      _inheritanceManager ??= new InheritanceManager(this, ignoreErrors: true);
 
   @override
   LibraryCycleForLink get libraryCycleForLink {
     if (!_libraryNode.isEvaluated) {
       new LibraryDependencyWalker().walk(_libraryNode);
     }
     return _libraryNode._libraryCycle;
   }
 
   /**
@@ skipping 1553 matching lines @@
    * there are no type parameters in scope.
    */
   TypeParameterizedElementMixin get _typeParameterContext;
 
   @override
   noSuchMethod(Invocation invocation) => super.noSuchMethod(invocation);
 
   @override
   String toString() => '$enclosingElement.$name';
 }