refactor: remove duplicated trim()

It is already trimmed in Line 415.

Author: kenjis

system/Database/BaseBuilder.php

@@ -424,7 +424,7 @@ public function select($select = '*', ?bool $escape = null)
                  * This prevents NULL being escaped
                  * @see https://github.com/codeigniter4/CodeIgniter4/issues/1169
                  */
-                if (mb_stripos(trim($val), 'NULL') === 0) {
+                if (mb_stripos($val, 'NULL') === 0) {
                     $this->QBNoEscape[] = false;
 
                     continue;