Fix CI_Security::get_random_bytes() length validation
diff --git a/system/core/Security.php b/system/core/Security.php
index bc224e7..782d3e8 100755
--- a/system/core/Security.php
+++ b/system/core/Security.php
@@ -559,7 +559,7 @@
 	 */
 	public function get_random_bytes($length)
 	{
-		if (empty($length) OR ! ctype_digit($length))
+		if (empty($length) OR ! ctype_digit((string) $length))
 		{
 			return FALSE;
 		}