fix repository::get non discrim resolves a boolean instead of the item

Author: SQKo

src/Discord/Repository/AbstractRepository.php

@@ -375,7 +375,8 @@ public function get(string $discrim, $key)
                 continue;
             }
 
-            if ($resolved = nowait($this->cache->get($offset)) !== null) {
+            $resolved = nowait($this->cache->get($offset));
+            if ($resolved !== null) {
                 return $resolved;
             }
             break;