Fix duplicate assertion error using Redis Store

lib/SimpleSAML/Store/Redis.php

@@ -70,7 +70,7 @@ class Redis extends Store
 
         $result = $this->redis->get("{$type}.{$key}");
 
-        if ($result === false) {
+        if ($result === false || $result === null) {
             return null;
         }
 

tests/lib/SimpleSAML/Store/RedisTest.php

@@ -48,7 +48,7 @@ class RedisTest extends \PHPUnit_Framework_TestCase
 
     public function getMocked($key)
     {
-        return array_key_exists($key, $this->config) ? $this->config[$key] : false;
+        return array_key_exists($key, $this->config) ? $this->config[$key] : null;
     }
 
     public function setMocked($key, $value)