You get a NullPointerException after you check if that object is not null. You sure this error log is from this code?
HashMap<UUID, QuestManager> playerQuests = Main.getQuests(); //get Main instance for static hashmap containing players and their quests...
Another way to do this is by calculating all the points where a particle will spawn and at the end teleport the player to the end...
at the end do you use 'saveConfig()'? If not, try that. Otherwise I don't know why its set to null.
Can you post what you have?
//to save inventory content
getConfig().set(path + ".content", inventory.getContents());
//this is an implementation to get the content...
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