Warning: preg_replace(): Compilation failed: unknown option bit(s) set at offset -1

I recently upgraded my dedicated server to Apache 2.4.6, MySQL 5.5.32, and PHP 5.4.21. Now on my website I get this error:

Warning: preg_replace(): Compilation failed: unknown option bit(s) set at offset -1 in /home/champion/public_html/wp-includes/shortcodes.php on line 295

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Here is the code from shortcodes.php on line 295:

$text = preg_replace("/[x{00a0}x{200b}]+/u", " ", $text);

Is the preg_replace function not compatible with the new PHP 5.4.21?