unit tests fail with 2.6.1

[François Kooman]

They still work with 2.6.0.

Possibly related to #44.

$ vendor/bin/phpunit --verbose
PHPUnit 9.5.20 #StandWithUkraine

Runtime:       PHP 8.1.6
Configuration: /home/X/Projects/constant_time_encoding/phpunit.xml.dist

.E.....E..........................................                50 / 50 (100%)

Time: 00:01.520, Memory: 12.00 MB

There were 2 errors:

1) ParagonIE\ConstantTime\Tests\Base32HexTest::testDecodeNoPadding
Uninitialized string offset 8

/home/X/Projects/constant_time_encoding/src/Base32.php:200
/home/X/Projects/constant_time_encoding/tests/Base32HexTest.php:59

2) ParagonIE\ConstantTime\Tests\Base32Test::testDecodeNoPadding
Uninitialized string offset 8

/home/X/Projects/constant_time_encoding/src/Base32.php:200
/home/X/Projects/constant_time_encoding/tests/Base32Test.php:80

ERRORS!
Tests: 50, Assertions: 49865, Errors: 2.

[P.I.E. Security Team]

Fixed in v2.6.2.