Wrong datatype for first argument in call to array_key_exists

I'm using Drupal 4.3.0 with locale module active.
There is a minor bug in locale.module. At line 343, that shows:
"Wrong datatype for first argument in call to array_key_exists"

This is the problem:

This is wrong:
if (is_array($locale_t) && array_key_exists($string, $locale_t)) {

This is correct:
if (is_array($locale_t) && !is_null($string) && array_key_exists($string, $locale_t)) {

-------------
Extracted from http://www.php.net/manual/es/function.array-key-exists.php:
...
In PHP 4.1.2, passing a NULL for the first parameter will result in an error:
Wrong datatype for first argument in call to array_key_exists
By 4.3.2 this message has been removed.
use short circuit operators to emulate the more current behavior under older versions of PHP:
(is_null($key) || !array_key_exists($key, $search))
...