Parsing: Impossible to differ between NULL and Empty Object

[flappingeagle]

Given following json:

{
	"tests": [
		{
			"o": null
		},
		{
			"o": {
				
			}
		}
	]
}

the following events are given for the parser for the above example:

START_DOCUMENT
PROCESSING_INSTRUCTION (xml-multiple:tests)
START_ELEMENT (tests)
START_ELEMENT (o)
END_ELEMENT (o)
END_ELEMENT (tests)
START_ELEMENT (tests)
START_ELEMENT (o)
END_ELEMENT (o)
END_ELEMENT (tests)
END_DOCUMENT

how can i differ between "o=null" and "o=Empty-Object" with the staxon-parser?