ExpAI: fix bug in finding hexes next to healers

The CA was supposed to mark hexes next to healers as potential healing locations, but because of this bug that did not work.

data/ai/lua/retreat.lua

@@ -98,7 +98,7 @@ function retreat_functions.get_healing_locations()
                     local old_values = healing_locs:get(x, y) or {0, 0}
                     local best_heal = math.max(old_values[0] or heal_amount)
                     local best_cure = math.max(old_values[1] or cure)
-                    healing_locs:insert(u.x, u.y, {best_heal, best_cure})
+                    healing_locs:insert(x, y, {best_heal, best_cure})
                 end
             end
         end