This might happen if the "title" of the file (the second line in the file) is empty. It's not a big problem, what's supposed to happen is that a tooltip pops up, showing the title (which is empty anyway for your file).
So, a tiny bug which we can fix, but nothing for you to worry about.
Thank you very much!
I do believe this is not a big bug. That is why I post it here.
The only thing I need to worry is that make sure do not move mouse to that kind obj.
One time move to it, only get a err window. But too much time or times on those objects, my VNL will crash, and what I can only do then is to reboot VNL.