Looks like you somehow scrolled the layout too far. Look at the bottom right corner on your screenshot - cursor position is at (-89565, -71618)
Try to set margins in layout properties to 100000x100000. Then scroll to (0,0) with mouse wheel and Shift+Mouse wheel.
EDIT: I may be wrong, I see that you zoomed out to 1%. Could be a bug, try opening this project in a different browser or on a different computer.