Merge pull request #1174 from FrancoisChaumont/fix--defined()-use-for…

…-function

fix: cannot override `emailer()` function

src/Helpers/email_helper.php

@@ -13,7 +13,7 @@
 
 use CodeIgniter\Email\Email;
 
-if (! defined('emailer')) {
+if (! function_exists('emailer')) {
     /**
      * Provides convenient access to the CodeIgniter Email class.
      *