More glitches - tabs not in sync with Chrome

Not major, but still seems a few things manage to slip through. Sorry I can't detail exactly how I arrived here - I had the 3 pinned tabs open, and then had one or 2 more open which I closed with a middle click in Sidewise. I think my trusty old Intellimouse might be developing a fault, because sometimes closing a tab in this way also creates a new blank tab - suspect the switch is bouncing. Anyway, this is what I ended up with:

Note the 'New Tab' in Chrome but not in Sidewise. I quick 'refresh' (with F5) on the Sidewise window normally gets things back - but this time the New Tab had an interesting favicon:

Maybe Sidewise is suggesting that I might like to start a new Wikipedia page about Sidewise?