added is_boundary for &out_of_bounds just in case

cell.cpp

@@ -1423,6 +1423,7 @@ EX int valence() {
 
 /** portalspaces are not defined outside of a boundary */
 EX bool is_boundary(cell *c) {
+  if(c == &out_of_bounds) return true;
   return (cgflags & qPORTALSPACE) && isWall(c->wall);
   }