It shows up to notify things to you because the left sidebar is hidden in all your tabs. If any tab has the left sidebar shown, the icon won't show up.
Indeed I have it closed. That's a little bit frustrating as I have no use for the left bar or the information that icon has told me.
Okay, I'll maybe figure out how to jigger my layout to include the left bar.
Thank you for the quick answer
Edit: It seems there's no way to not have the navigator included in the left bar, which seems to be the reason why I disabled it to begin with as I really don't want the navigator. Oh well, I'll live with that random appearing icon.