fix test

Do not yield Redis Sentinel test data if the required environment variables
are not configured.

Author: xabbuh

src/Symfony/Component/Messenger/Bridge/Redis/Tests/Transport/RedisTransportFactoryTest.php

@@ -66,10 +66,12 @@ public static function createTransportProvider(): iterable
             ['stream' => 'bar', 'delete_after_ack' => true],
         ];
 
-        yield 'redis_sentinel' => [
-            'redis:?host['.str_replace(' ', ']&host[', getenv('REDIS_SENTINEL_HOSTS')).']',
-            ['sentinel_master' => getenv('REDIS_SENTINEL_SERVICE')],
-        ];
+        if (false !== getenv('REDIS_SENTINEL_HOSTS') && false !== getenv('REDIS_SENTINEL_SERVICE')) {
+            yield 'redis_sentinel' => [
+                'redis:?host['.str_replace(' ', ']&host[', getenv('REDIS_SENTINEL_HOSTS')).']',
+                ['sentinel_master' => getenv('REDIS_SENTINEL_SERVICE')],
+            ];
+        }
     }
 
     private function skipIfRedisUnavailable()