cannot assert that free_unit has no faction (complicated reasons)

src/kernel/region.c

@@ -917,6 +917,7 @@ void free_region(region * r)
     while (r->units) {
         unit *u = r->units;
         r->units = u->next;
+        u->region = NULL;
         uunhash(u);
         free_unit(u);
         free(u);

src/kernel/unit.c

@@ -1400,12 +1400,11 @@ int invisible(const unit * target, const unit * viewer)
 /** remove the unit from memory.
  * this frees all memory that's only accessible through the unit,
  * and you should already have called uunhash and removed the unit from the
- * region and faction.
+ * region.
  */
 void free_unit(unit * u)
 {
     assert(!u->region);
-    assert(!u->faction);
     free(u->_name);
     free(u->display);
     free_order(u->thisorder);