Merge pull request #34342 from nextcloud/backport/34328/stable23

[stable23] Correctly handle Redis::keys returning false

Author: blizzz

build/stubs/redis.php

@@ -2177,7 +2177,7 @@ public function pExpireAt($key, $timestamp)
      *
      * @param string $pattern pattern, using '*' as a wildcard
      *
-     * @return array string[] The keys that match a certain pattern.
+     * @return string[]|false The keys that match a certain pattern.
      *
      * @link    https://redis.io/commands/keys
      * @example

lib/private/Memcache/Redis.php

@@ -128,7 +128,7 @@ public function clear($prefix = '') {
 		$keys = self::$cache->keys($prefix);
 		$deleted = self::$cache->del($keys);
 
-		return count($keys) === $deleted;
+		return (is_array($keys) && (count($keys) === $deleted));
 	}
 
 	/**