guard against null staticInvokeType

pkg/analyzer/lib/src/generated/element_resolver.dart

 // Copyright (c) 2014, 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.src.generated.element_resolver;
 
 import 'dart:collection';
 
 import 'package:analyzer/dart/element/element.dart';
 import 'package:analyzer/dart/element/type.dart';
@@ skipping 635 matching lines @@
         _computeMethodInvokeType(node, propagatedElement);
 
     //
     // Record the results.
     //
     methodName.staticElement = staticElement;
     methodName.propagatedElement = propagatedElement;
 
     node.staticInvokeType = staticInvokeType;
     if (propagatedInvokeType != null &&
-        propagatedInvokeType.isMoreSpecificThan(staticInvokeType)) {
+        (staticInvokeType == null ||
+            propagatedInvokeType.isMoreSpecificThan(staticInvokeType))) {
       // Don't store the propagated invoke type unless it's more specific than
       // the static type. We still need to record the propagated parameter
       // elements however, as that is used for the propagatedType downwards
       // inference of lambda parameters.
       node.propagatedInvokeType = propagatedInvokeType;
     } else {
       node.propagatedInvokeType = null;
     }
 
     ArgumentList argumentList = node.argumentList;
@@ skipping 1902 matching lines @@
 
   @override
   Element get staticElement => null;
 
   @override
   accept(AstVisitor visitor) => null;
 
   @override
   void visitChildren(AstVisitor visitor) {}
 }