fix(mdns): Fixed dead-code reported by coverity

Fixes CID 467738: Logically dead code in mdns.c, _copy_mdns_txt_items
Introduced by probably by a merge confilict, as the fix was added in
two separate PRs, merging d4da9cb first and 8a69050 later

Author: david-cermak

components/mdns/mdns.c

@@ -5956,11 +5956,6 @@ static mdns_txt_item_t *_copy_mdns_txt_items(mdns_txt_linked_item_t *items, uint
     for (mdns_txt_linked_item_t *tmp = items; tmp != NULL; tmp = tmp->next) {
         ret_index++;
     }
-    if (ret_index == 0) {
-        *txt_count = 0;
-        *txt_value_len = NULL;
-        return NULL;
-    }
     *txt_count = ret_index;
     if (ret_index == 0) {   // handle empty TXT
         *txt_value_len = NULL;