[turbofan] Fixed segmentation fault while printing TurboFan node

src/compiler/node.cc

 // Copyright 2013 the V8 project authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "src/compiler/node.h"
 
 namespace v8 {
 namespace internal {
 namespace compiler {
 
@@ skipping 351 matching lines @@
 }
 #endif
 
 
 std::ostream& operator<<(std::ostream& os, const Node& n) {
   os << n.id() << ": " << *n.op();
   if (n.InputCount() > 0) {
     os << "(";
     for (int i = 0; i < n.InputCount(); ++i) {
       if (i != 0) os << ", ";
-      os << n.InputAt(i)->id();
+      if (n.InputAt(i)) {
+        os << n.InputAt(i)->id();
+      } else {
+        os << "null";
+      }
     }
     os << ")";
   }
   return os;
 }
 
 
 Node::InputEdges::iterator Node::InputEdges::iterator::operator++(int n) {
   iterator result(*this);
   ++(*this);
@@ skipping 29 matching lines @@
   ++(*this);
   return result;
 }
 
 
 bool Node::Uses::empty() const { return begin() == end(); }
 
 }  // namespace compiler
 }  // namespace internal
 }  // namespace v8