butterflies: log message when ending debug run early

src/modules/butterflies/butterflies_dispersal.c

@@ -42,6 +42,7 @@ static void inline single_random_walk(struct cats_thread_info *ts, struct cats_g
         const struct conf_data_butterflies *module_conf = CATS_MODULE_DATA;
         const bool debug_rw = module_conf->debug_rw;
 
+
         int32_t eggs_left = eggs;
         const cats_dt_coord max_steps = module_conf->animal_dispersal_max_radius;
 
@@ -71,6 +72,7 @@ static void inline single_random_walk(struct cats_thread_info *ts, struct cats_g
                         return; // we escaped the simulation extent and got lost
                 }
 
+
                 // is the cell a valid dispersal target location?
                 if (!(data->info_layer[row][col] & BF_CELL_VALID_DISPERSAL_TARGET)) {
                         if (debug_rw) {
@@ -220,6 +222,7 @@ butterflies_cell_dispersal(struct cats_grid *grid, struct cats_thread_info *ts,
         if (debug_rw) {
                 fflush(module_conf->debug_rw_file);
                 fclose(module_conf->debug_rw_file);
+                log_message(LOG_IMPORTANT, "Ending simulation early - first cell with random walks complete");
                 exit_cats(EXIT_SUCCESS);
         }
 }
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