Question

An AI wrote this Kotlin code in an Android mobile game to look up a level's config and start it. It works for the campaign levels the dev tested, but crashes with a NullPointerException when players reach community-made or seasonal levels. What's the bug and how would you catch it?

1fun startLevel(id: String) {2    val config = levelConfigs[id]!!            // map lookup, force non-null3    val music = soundtracks[config.themeId]!!  // nested lookup4    audio.play(music)5    engine.load(config)6}