TokenType#toString returned null

FULL PRODUCT VERSION :


ADDITIONAL OS VERSION INFORMATION :
Linux uchida-CM6870 3.8.0-26-generic #38-Ubuntu SMP Mon Jun 17 21:43:33 UTC 2013 x86_64 x86_64 x86_64 GNU/Linux

EXTRA RELEVANT SYSTEM CONFIGURATION :
I built in reference to this:
https://wiki.openjdk.java.net/display/Nashorn/Building+Nashorn

A DESCRIPTION OF THE PROBLEM :
Nashorn's bug tracker is this here?

I like Rhino Parer and AST. So I expect that Nashorn still use it.
When I ran the code like this:
```
var ir = Packages.jdk.nashorn.internal.ir;
var runtime = Packages.jdk.nashorn.internal.runtime;
var parser = Packages.jdk.nashorn.internal.parser;

var context = runtime.Context.getContext();
var source = new runtime.Source('test', function() {
  if (1) {
    print('hoge');
  } else {
    print(1 + 2);
  }
}.toString());

var node = new parser.Parser(context.getEnv(), source, new runtime.Context.ThrowErrorManager(), true).parse();
var lexContext = new ir.LexicalContext();
node.accept(lexContext, new ir.visitor.NodeVisitor(lexContext) {
  enterDefault: function(node) {
    print(node.tokenType()/*.toString()*/ + ': ' + node);
    return true;
  }
});
```

got error:
```
$ ./build/linux-x86_64-normal-server-release/images/j2sdk-image/bin/jjs ~/tmp/visitor.js
function: [<unknown>] function runScript()
function: var _L1 = [<unknown>] function _L1();
function: var _L1 = [<unknown>] function _L1()
function: _L1
{: [<unknown>] function _L1()
{: if (1);
if: if (1)
Exception in thread " main " java.lang.NullPointerException
at jdk.nashorn.internal.runtime.ConsString.<init>(ConsString.java:55)
at jdk.nashorn.internal.runtime.ScriptRuntime.ADD(ScriptRuntime.java:547)
at jdk.nashorn.internal.scripts.Script$visitor._L17(/home/uchida/tmp/visitor.js:18)
at jdk.nashorn.internal.ir.visitor.NodeVisitor$$NashornJavaAdapter.enterDefault(Unknown Source)
at jdk.nashorn.internal.ir.visitor.NodeVisitor.enterLiteralNode(NodeVisitor.java:478)
at jdk.nashorn.internal.ir.visitor.NodeVisitor$$NashornJavaAdapter.enterLiteralNode(Unknown Source)
at jdk.nashorn.internal.ir.LiteralNode.accept(LiteralNode.java:215)
at jdk.nashorn.internal.ir.IfNode.accept(IfNode.java:78)
at jdk.nashorn.internal.ir.Node.accept(Node.java:291)
at jdk.nashorn.internal.ir.Block.accept(Block.java:139)
at jdk.nashorn.internal.ir.LexicalContextNode$Acceptor.accept(LexicalContextNode.java:51)
at jdk.nashorn.internal.ir.Block.accept(Block.java:344)
at jdk.nashorn.internal.ir.FunctionNode.accept(FunctionNode.java:297)
at jdk.nashorn.internal.ir.LexicalContextNode$Acceptor.accept(LexicalContextNode.java:51)
at jdk.nashorn.internal.ir.LexicalContextExpression.accept(LexicalContextExpression.java:46)
at jdk.nashorn.internal.ir.FunctionNode.accept(FunctionNode.java:49)
at jdk.nashorn.internal.ir.VarNode.accept(VarNode.java:127)
at jdk.nashorn.internal.ir.Node.accept(Node.java:291)
at jdk.nashorn.internal.ir.Block.accept(Block.java:139)
at jdk.nashorn.internal.ir.LexicalContextNode$Acceptor.accept(LexicalContextNode.java:51)
at jdk.nashorn.internal.ir.Block.accept(Block.java:344)
at jdk.nashorn.internal.ir.FunctionNode.accept(FunctionNode.java:297)
at jdk.nashorn.internal.scripts.Script$visitor.runScript(/home/uchida/tmp/visitor.js:16)
at jdk.nashorn.internal.runtime.ScriptFunctionData.invoke(ScriptFunctionData.java:518)
at jdk.nashorn.internal.runtime.ScriptFunction.invoke(ScriptFunction.java:204)
at jdk.nashorn.internal.runtime.ScriptRuntime.apply(ScriptRuntime.java:366)
at jdk.nashorn.tools.Shell.apply(Shell.java:386)
at jdk.nashorn.tools.Shell.runScripts(Shell.java:315)
at jdk.nashorn.tools.Shell.run(Shell.java:179)
at jdk.nashorn.tools.Shell.main(Shell.java:143)
at jdk.nashorn.tools.Shell.main(Shell.java:122)
```

jdk.nashorn.internal.parser.TokenType#toString may returned null.



REPRODUCIBILITY :
This bug can be reproduced always.