Descriptive Problem Summary:
When a player is standing near the edge of a map and world.maxx or world.maxy is lowered, any tiles out of the new map boundary will not update. Rather than turfs turning black they will continue to display the old turf until the player moves out of view then moves back to the edge of the map.

Numbered Steps to Reproduce Problem:
Stand near the edge of the map with the "void" in view.
Lower world.maxx or world.maxy so some of the map within view is deleted. (Make sure not to delete yourself!)
The turfs which used to be the edge of the map which are now deleted are still displayed.

Expected Results:
The turfs lost from lowering the map boundaries should vanish.

Actual Results:
The turfs are still displayed until a player moves out of view.