fix npe part 2

src/main/java/cc/fascinated/bat/common/UserUtils.java

@@ -23,7 +23,7 @@ public class UserUtils {
             log.error("Failed to find user \"{}\" after {} retries.", id, retries);
             return null;
         }
-        User user = DiscordService.JDA.getUserById(id);
+        User user = DiscordService.JDA.retrieveUserById(id).complete();
         if (user == null) {
             return getUser(id, retries + 1);
         }