@Trogl - I wrote up a reply, but I think I have forgotten to click "Post".
Basically, my post said "I tested this, and I couldn't reproduce it."
But now looking at this again, it makes a bit more sense to me why you're experiencing it.
Looking through the code - delete definitely clears the name and stuff. The line in there is because the slot internally is still there.
The clip should be cleared & empty though, so it shouldn't cause any issues, apart from that ugly line in there, and when you iterate through clips, you will find empty clips in there.
The next time you create a clip, it will occupy this slot, though.
So, it isn't really a bug, but not ideal behaviour either. It will change in a future version.