Starting with ForeFlight 8, the World Map layer is gone. It has been replaced by a worldwide base map that is always displayed underneath any selected chart. This means if you pan off of the edge of a selected aeronautical chart, you'll will still see map data because of the base map.
If you have a Basic Plus or Pro Plus subscription, to display a view similar to the old World Map, tap the Maps drop-down in the upper left of the Maps page and de-select the Aeronautical layer.
If you have a Basic or Pro subscription (which cannot access the Aeronautical layer) you can display a simple view similar to the old World Map by de-selecting all charts in the Maps drop-down.