Fixed implicitly nullable params (#6616)

Author: huangdijia

src/Driver/DriverInterface.php

@@ -48,12 +48,12 @@ public function consume(): void;
     /**
      * Reload failed message into waiting queue.
      */
-    public function reload(string $queue = null): int;
+    public function reload(?string $queue = null): int;
 
     /**
      * Delete all failed message from failed queue.
      */
-    public function flush(string $queue = null): bool;
+    public function flush(?string $queue = null): bool;
 
     /**
      * Return info for current queue.

src/Driver/RedisDriver.php

@@ -109,7 +109,7 @@ public function fail(mixed $data): bool
         return false;
     }
 
-    public function reload(string $queue = null): int
+    public function reload(?string $queue = null): int
     {
         $channel = $this->channel->getFailed();
         if ($queue) {
@@ -127,7 +127,7 @@ public function reload(string $queue = null): int
         return $num;
     }
 
-    public function flush(string $queue = null): bool
+    public function flush(?string $queue = null): bool
     {
         $channel = $this->channel->getFailed();
         if ($queue) {