Debug NPE

when i use //debug and then i want to close the debug tab cant be closed and throws this
[03:32:01] C:\Users\savva\Desktop\BETA Server\game\data\scripts\quests\QuestMasterHandler.java
java.lang.StringIndexOutOfBoundsException: String index out of range: -1
        at java.lang.String.substring(Unknown Source)
        at quests.Q00255_Tutorial.Q00255_Tutorial.onTutorialEvent(Q00255_Tutorial.java:177)
        at com.l2jserver.gameserver.model.quest.Quest.notifyTutorialEvent(Quest.java:585)
        at com.l2jserver.gameserver.model.quest.Quest.lambda$registerTutorialEvent$57(Quest.java:2905)
        at com.l2jserver.gameserver.model.events.listeners.ConsumerEventListener.executeEvent(ConsumerEventListener.java:46)
        at com.l2jserver.gameserver.model.events.EventDispatcher.notifyToListeners(EventDispatcher.java:242)
        at com.l2jserver.gameserver.model.events.EventDispatcher.notifyEventToMultipleContainers(EventDispatcher.java:186)
        at com.l2jserver.gameserver.model.events.EventDispatcher.lambda$notifyEventAsync$0(EventDispatcher.java:121)
        at com.l2jserver.gameserver.ThreadPoolManager$RunnableWrapper.run(ThreadPoolManager.java:89)
        at java.util.concurrent.ThreadPoolExecutor.runWorker(Unknown Source)
        at java.util.concurrent.ThreadPoolExecutor$Worker.run(Unknown Source)
        at java.lang.Thread.run(Unknown Source)
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