Update lib/private/Memcache/KeyValueCache.php

Co-authored-by: Kate <26026535+provokateurin@users.noreply.github.com>
Signed-off-by: Ferdinand Thiessen <opensource@fthiessen.de>

Author: susnux

lib/private/Memcache/KeyValueCache.php

@@ -49,10 +49,7 @@ class KeyValueCache extends Cache implements IMemcacheTTL {
 	private ?Client $cache = null;
 
 	public function getCache(): Client {
-		if ($this->cache === null) {
-			$this->cache = Server::get(KeyValueCacheFactory::class)->getInstance();
-		}
-		return $this->cache;
+		return $this->cache ??= Server::get(KeyValueCacheFactory::class)->getInstance();
 	}
 
 	#[\Override]