When an item from globalStorage is removed by a way other then call to removeItem, then JS engine returns the last known value for a property instead of null. Looks like nsStorageSH::GetNamedItem has to return an object with a null value inside. Because when nsStorageSH::GetNamedItem retuns null, vp is not updated in nsNamedArraySH::GetProperty.

https://bugzilla.mozilla.org/show_bug.cgi?id=1472046 Move all DOM bugs that haven’t been updated in more than 3 years and has no one currently assigned to P5. If you have questions, please contact :mdaly.