Helper ast node sequences must not wrongly grab ownership of the enclosing

runtime/vm/opt_code_generator_ia32.cc

 // Copyright (c) 2011, 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_IA32.
 #if defined(TARGET_ARCH_IA32)
 
 #include "vm/opt_code_generator.h"
 
 #include "vm/assembler_macros.h"
@@ skipping 2549 matching lines @@
     return;
   }
   ASSERT(!IsResultNeeded(node));
   ASSERT(node->value() != NULL);
   VisitLoadOne(node->value(), EAX);
   GenerateReturnEpilog();
 }
 
 
 void OptimizingCodeGenerator::VisitSequenceNode(SequenceNode* node_sequence) {
-  if (FLAG_enable_type_checks ||
-      (node_sequence->scope()->num_context_variables() > 0)) {
+  const intptr_t num_context_variables = (node_sequence->scope() != NULL) ?
+      node_sequence->scope()->num_context_variables() : 0;
+  if (FLAG_enable_type_checks || (num_context_variables > 0)) {
     CodeGenerator::VisitSequenceNode(node_sequence);
     return;
   }
   for (int i = 0; i < node_sequence->length(); i++) {
     AstNode* child_node = node_sequence->NodeAt(i);
     state()->set_root_node(child_node);
     child_node->Visit(this);
   }
   if (node_sequence->label() != NULL) {
     __ Bind(node_sequence->label()->break_label());
@@ skipping 12 matching lines @@
   if (IsResultNeeded(node)) {
     // The result is the input value.
     __ pushl(EAX);
   }
 }
 
 
 }  // namespace dart
 
 #endif  // defined TARGET_ARCH_IA32