Merge pull request #468 from magarzon/bugfix/null_payload_in_reserve

In reserve method, if the payload is null, throws an error in PHP 8.1

src/drivers/redis/Queue.php

@@ -149,6 +149,10 @@ protected function reserve($timeout)
         }
 
         $payload = $this->redis->hget("$this->channel.messages", $id);
+        if (null === $payload) {
+            return null;
+        }
+
         list($ttr, $message) = explode(';', $payload, 2);
         $this->redis->zadd("$this->channel.reserved", time() + $ttr, $id);
         $attempt = $this->redis->hincrby("$this->channel.attempts", $id, 1);