Deleteting static function twice revives property with undefined

[Yusuke Suzuki]

RegExp.prototype.hasOwnProperty('exec');  // true
delete RegExp.prototype.exec;  // true
RegExp.prototype.hasOwnProperty('exec');  // false
delete RegExp.prototype.exec;  // true
RegExp.prototype.hasOwnProperty('exec');  // true ???

This is because JSObject::deleteProperty set undefine by `putEntry` if `isValidOffset(...)` is false (deleted).

[Yusuke Suzuki]

We'll fix this with issue 145705.

*** This bug has been marked as a duplicate of bug 145705 ***