Fix merge error, Debug_StepInto test

runtime/vm/code_patcher_x64.cc

 // 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.
 
 #include "vm/globals.h"  // Needed here to get TARGET_ARCH_X64.
 #if defined(TARGET_ARCH_X64)
 
 #include "vm/assembler.h"
 #include "vm/code_patcher.h"
 #include "vm/cpu.h"
@@ skipping 211 matching lines @@
                                     int* num_named_arguments,
                                     uword* target) {
   ASSERT(num_arguments != NULL);
   ASSERT(num_named_arguments != NULL);
   ASSERT(target != NULL);
   InstanceCall call(return_address);
   *num_arguments = call.argument_count();
   *num_named_arguments = call.named_argument_count();
   *target = call.target();
   const ICData& ic_data = ICData::Handle(call.ic_data());
-  *function_name = ic_data.target_name();
+  if (function_name != NULL) {
+    *function_name = ic_data.target_name();
+  }
 }
 
 
 RawICData* CodePatcher::GetInstanceCallIcDataAt(uword return_address) {
   InstanceCall call(return_address);
   return call.ic_data();
 }
 
 
 intptr_t CodePatcher::InstanceCallSizeInBytes() {
   return DartCallPattern::kCallPatternSize;
 }
 
 }  // namespace dart
 
 #endif  // defined TARGET_ARCH_X64