Only trigger an emergency sort of the stars after star formation if we are...

Only trigger an emergency sort of the stars after star formation if we are running with feedback (and hence need sorted stars).

src/runner.c

@@ -573,6 +573,7 @@ void runner_do_star_formation(struct runner *r, struct cell *c, int timer) {
   struct part *restrict parts = c->hydro.parts;
   struct xpart *restrict xparts = c->hydro.xparts;
   const int with_cosmology = (e->policy & engine_policy_cosmology);
+  const int with_feedback = (e->policy & engine_policy_feedback);
   const struct hydro_props *restrict hydro_props = e->hydro_properties;
   const struct unit_system *restrict us = e->internal_units;
   struct cooling_function_data *restrict cooling = e->cooling_func;
@@ -648,7 +649,8 @@ void runner_do_star_formation(struct runner *r, struct cell *c, int timer) {
 
   /* If we formed any stars, the star sorts are now invalid. We need to
    * re-compute them. */
-  if ((c == c->hydro.super) && (current_stars_count != c->stars.count)) {
+  if (with_feedback && (c == c->hydro.super) &&
+      (current_stars_count != c->stars.count)) {
     cell_clear_stars_sort_flags(c, /*is_super=*/1);
     runner_do_stars_sort(r, c, 0x1FFF, /*cleanup=*/0, /*timer=*/0);
   }