Why is ItemPath in ExecutionLog3 sometimes null/blank

I think the ExecutionLog3 view is an exceptionally good feature! 

However I don't understand why is ItemPath field allowed to be NULL.

When I query the View. I see a lot of times where an item with NULL itempath has taken lot of processing, render and data fetch time. but pity there is no way to know who that item was because ItemPath is null. 

MSDNStudent Knows not much!