BESEN undefined accessor properties bug

besenTest.js

// BESEN strange behavior on named accessor property
// Tested on r77

var obj = Object.defineProperty({}, 'foo', { set: undefined }),
    desc = Object.getOwnPropertyDescriptor(obj, 'foo');

// Definning a setter just to make the property a named accessor property.
// (`undefined` is a valid value for the [[Set]] and [[Get]] property attributes)

// the getter is correctly `undefined`, the FromPropertyDescriptor
// and ToPropertyDescriptor  abstract operations are working properly,
// (BTW, Chrome 5, 6dev and Safari 5 fail to even create the property ;) 

print(desc.hasOwnProperty('get') && desc.get === undefined); // 1. true

// [[Put]]/[[CanPut]] also work propertly, an asssignment 
// simply fails silently on non-strict code, [[CanPut]] 
// just returns `false` (Sect. 8.12.4, Step 2.a.i)

obj.foo = 'bar';

// But [[Get]](P) should explicitly return `undefined` if the
// getter of an accessor property is `undefined` as described
// in the section 8.12.3 (on the wrongly numbered step 12):

print(obj.foo); // 2. "reference", no clue about this
print(typeof obj.foo); // 3. "undefined" as expected, but:
print(obj.foo === undefined); // 4. false
try {
  obj.foo+''; // 5. "TypeError: Bad to string conversation"       
} catch (e) { // I thought that print made ToString convertion
  print(e);
}