Error: 
  A LEAK is a hole in the map, where the inside of it is exposed to the
(unwanted) outside region.  The entity listed in the error is just a helpful
indication of where the beginning of the leak pointfile starts, so the
beginning of the line can be quickly found and traced to until reaching the
outside. Unless this entity is accidentally on the outside of the map, it
probably should not be deleted.  Some complex rotating objects entities need
their origins outside the map.  To deal with these, just enclose the origin
brush with a solid world brush

Leak pointfile generated