Fix inferMethodInvocation in the case where interfaceMember is null.

pkg/front_end/lib/src/fasta/kernel/kernel_shadow_ast.dart

 // Copyright (c) 2017, 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 file declares a "shadow hierarchy" of concrete classes which extend
 /// the kernel class hierarchy, adding methods and fields needed by the
 /// BodyBuilder.
 ///
 /// Instances of these classes may be created using the factory methods in
 /// `ast_factory.dart`.
@@ skipping 1811 matching lines @@
   @override
   void _collectDependencies(KernelDependencyCollector collector) {
     // Super expressions should never occur in top level type inference.
     // TODO(paulberry): but could they occur due to invalid code?
     assert(false);
   }
 
   @override
   DartType _inferExpression(
       KernelTypeInferrer inferrer, DartType typeContext, bool typeNeeded) {
-    inferrer.instrumentation?.record(Uri.parse(inferrer.uri), fileOffset,
-        'target', new InstrumentationValueForMember(interfaceTarget));
+    if (interfaceTarget != null) {
+      inferrer.instrumentation?.record(Uri.parse(inferrer.uri), fileOffset,
+          'target', new InstrumentationValueForMember(interfaceTarget));
+    }
     return inferrer.inferMethodInvocation(this, new KernelThisExpression(),
         fileOffset, false, typeContext, typeNeeded,
         interfaceMember: interfaceTarget,
         methodName: name,
         arguments: arguments);
   }
 }
 
 /// Shadow object for [SuperPropertyGet].
 class KernelSuperPropertyGet extends SuperPropertyGet
@@ skipping 511 matching lines @@
   }
 
   transformChildren(v) {
     return internalError("Internal error: Unsupported operation.");
   }
 
   visitChildren(v) {
     return internalError("Internal error: Unsupported operation.");
   }
 }