Ah, that's not supposed to be there like that indeed. I'll probably need to snoop around Godot forums to figure out how to test/avoid this on other machines. In the project and my system the entire screen space is utilized. Thanks for spotting it!
212 days ago(+1)
Probably has to do with the stretching. Try changing the values in Display->Window->Stretch
You can replicate this by resizing your windows, or zooming your browser page to other than 100%