Update invariant for unresolved (static) get.

pkg/compiler/lib/src/ssa/builder.dart

 // 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.
 
 part of ssa;
 
 class SsaFunctionCompiler implements FunctionCompiler {
   SsaCodeGeneratorTask generator;
   SsaBuilderTask builder;
   SsaOptimizerTask optimizer;
@@ skipping 3280 matching lines @@
   /// Generate read access of an unresolved static or top level entity.
   void generateStaticUnresolvedGet(ast.Send node, Element element) {
     if (element is ErroneousElement) {
       // An erroneous element indicates an unresolved static getter.
       generateThrowNoSuchMethod(
           node,
           noSuchMethodTargetSymbolString(element, 'get'),
           argumentNodes: const Link<ast.Node>());
     } else {
       // This happens when [element] has parse errors.
-      assert(invariant(node, element.isErroneous));
+      assert(invariant(node, element == null || element.isErroneous));
       // TODO(ahe): Do something like the above, that is, emit a runtime
       // error.
       stack.add(graph.addConstantNull(compiler));
     }
   }
 
   /// Read a static or top level [field] of constant value.
   void generateStaticConstGet(
       ast.Send node,
       FieldElement field,
@@ skipping 4532 matching lines @@
     if (unaliased is TypedefType) throw 'unable to unalias $type';
     unaliased.accept(this, builder);
   }
 
   void visitDynamicType(DynamicType type, SsaBuilder builder) {
     JavaScriptBackend backend = builder.compiler.backend;
     ClassElement cls = backend.findHelper('DynamicRuntimeType');
     builder.push(new HDynamicType(type, new TypeMask.exact(cls, classWorld)));
   }
 }