document.getElementByID - checking whether an element has been found or not

Question

Hi, guys.

Here's a sample code, that opens an internet explorer window, navigates to google, and gets some element on the page by its unique id:

set ie = CreateObject("InternetExplorer.Application")

ie.navigate("www.google.com")
ie.visible = true

while ie.readystate <> 4
    wscript.sleep 100
WEnd

set some_object = ie.document.getelementbyid("xjsc")

MsgBox some_object.tagname, 0

This sample brings me a DIV popup, which satisfies me completely.

But at the next step I'd like to check whether some id exists in the page, or not. Unfortunately, I can't just be, like,

set some_object = ie.document.getelementbyid("some_non_existant_id")
if some_object.tagname = "" then
...

because it gives me the following error:

ie.vbs(12, 1) Microsoft VBScript runtime error: Object required: 'some_object'

So, what's the best practice to check whether an element has been found or not?