I'm having this problem where after I create a quest, under specific, unknown circumstances, I cannot edit it again. Here are the logs when I execute the command:

[18:45:17 INFO]: Zalakoth issued server command: /quests editor
«types to edit quests»
«types Quest name ("Tutorial")»
[18:45:21 ERROR]: Error handling conversation prompt
java.lang.IndexOutOfBoundsException: Index: 0, Size: 0
at java.util.LinkedList.checkElementIndex(LinkedList.java:555) ~[?:1.8.0_91]
at java.util.LinkedList.get(LinkedList.java:476) ~[?:1.8.0_91]
at me.blackvein.quests.Stage$3.equals(Stage.java:104) ~[?:?]
at me.blackvein.quests.Stage.equals(Stage.java:236) ~[?:?]
at java.util.LinkedList.indexOf(LinkedList.java:605) ~[?:1.8.0_91]
at me.blackvein.quests.QuestFactory.loadQuest(QuestFactory.java:1895) ~[?:?]
at me.blackvein.quests.QuestFactory$SelectEditPrompt.acceptInput(QuestFactory.java:458) ~[?:?]
at org.bukkit.conversations.Conversation.acceptInput(Conversation.java:229) [spigot-1.9.4.jar:git-Spigot-8a048fe-d8637df]
at org.bukkit.craftbukkit.v1_9_R2.conversations.ConversationTracker.acceptConversationInput(ConversationTracker.java:58) [spigot-1.9.4.jar:git-Spigot-8a048fe-d8637df]
at org.bukkit.craftbukkit.v1_9_R2.entity.CraftPlayer.acceptConversationInput(CraftPlayer.java:1029) [spigot-1.9.4.jar:git-Spigot-8a048fe-d8637df]
at net.minecraft.server.v1_9_R2.PlayerConnection$5.evaluate(PlayerConnection.java:1198) [spigot-1.9.4.jar:git-Spigot-8a048fe-d8637df]
at org.bukkit.craftbukkit.v1_9_R2.util.Waitable.run(Waitable.java:24) [spigot-1.9.4.jar:git-Spigot-8a048fe-d8637df]
at net.minecraft.server.v1_9_R2.MinecraftServer.D(MinecraftServer.java:740) [spigot-1.9.4.jar:git-Spigot-8a048fe-d8637df]
at net.minecraft.server.v1_9_R2.DedicatedServer.D(DedicatedServer.java:399) [spigot-1.9.4.jar:git-Spigot-8a048fe-d8637df]
at net.minecraft.server.v1_9_R2.MinecraftServer.C(MinecraftServer.java:665) [spigot-1.9.4.jar:git-Spigot-8a048fe-d8637df]
at net.minecraft.server.v1_9_R2.MinecraftServer.run(MinecraftServer.java:564) [spigot-1.9.4.jar:git-Spigot-8a048fe-d8637df]
at java.lang.Thread.run(Thread.java:745) [?:1.8.0_91]

Version 2.6.0 AND 2.6.1 both have the problem listed.

NOTES: (Or at least what I have found so far.)

It happens when I have a start or end message to an objective...
When I have a "Talk to NPC" objective... (Which is also broken gameplay-wise.)

@Zalakoth Please try Quests 2.6.4 and post the "new" error if still an issue. Also, please upload your quests.yml for testing.

Closing due to lack of response from OP. If this is still an issue, follow my previous suggestion with the latest version of Quests. Thanks!