[ci skip] Proper error handling for Sessions on PHP 5

This was actually a PHP bug, see https://wiki.php.net/rfc/session.user.return-value

Also related: #4039
diff --git a/user_guide_src/source/changelog.rst b/user_guide_src/source/changelog.rst
index f4e5158..caa4455 100644
--- a/user_guide_src/source/changelog.rst
+++ b/user_guide_src/source/changelog.rst
@@ -25,6 +25,7 @@
 -  Fixed a bug (#4283) - :doc:`String Helper <helpers/string_helper>` function :php:func:`alternator()` couldn't be called without arguments.
 -  Fixed a bug (#4306) - :doc:`Database <database/index>` method ``version()`` didn't work properly with the 'mssql' driver.
 -  Fixed a bug (#4039) - :doc:`Session Library <libraries/sessions>` could generate multiple (redundant) warnings in case of a read failure with the 'files' driver, due to a bug in PHP.
+-  Fixed a bug where :doc:`Session Library <libraries/sessions>` didn't have proper error handling on PHP 5 (due to a PHP bug).
 
 Version 3.0.3
 =============