New Error message

16:19:54 ERROR]: Could not pass event AsyncPlayerChatEvent to VentureChat v2.15.1
org.bukkit.event.EventException: null
        at org.bukkit.plugin.java.JavaPluginLoader$1.execute(JavaPluginLoader.java:306) ~[spigot-1.12.2.jar:git-Spigot-dcd1643-e60fc34]
        at org.bukkit.plugin.RegisteredListener.callEvent(RegisteredListener.java:62) ~[spigot-1.12.2.jar:git-Spigot-dcd1643-e60fc34]
        at org.bukkit.plugin.SimplePluginManager.fireEvent(SimplePluginManager.java:500) [spigot-1.12.2.jar:git-Spigot-dcd1643-e60fc34]
        at org.bukkit.plugin.SimplePluginManager.callEvent(SimplePluginManager.java:482) [spigot-1.12.2.jar:git-Spigot-dcd1643-e60fc34]
        at net.minecraft.server.v1_12_R1.PlayerConnection.chat(PlayerConnection.java:1321) [spigot-1.12.2.jar:git-Spigot-dcd1643-e60fc34]
        at net.minecraft.server.v1_12_R1.PlayerConnection.a(PlayerConnection.java:1259) [spigot-1.12.2.jar:git-Spigot-dcd1643-e60fc34]
        at net.minecraft.server.v1_12_R1.PacketPlayInChat$1.run(PacketPlayInChat.java:39) [spigot-1.12.2.jar:git-Spigot-dcd1643-e60fc34]
        at java.util.concurrent.Executors$RunnableAdapter.call(Executors.java:511) [?:1.8.0_191]
        at java.util.concurrent.FutureTask.run(FutureTask.java:266) [?:1.8.0_191]
        at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1149) [?:1.8.0_191]
        at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:624) [?:1.8.0_191]
        at java.lang.Thread.run(Thread.java:748) [?:1.8.0_191]
Caused by: java.lang.StringIndexOutOfBoundsException: String index out of range: -1
        at java.lang.String.substring(String.java:1967) ~[?:1.8.0_191]
        at mineverse.Aust1n46.chat.utilities.Format.convertPlaceholders(Format.java:165) ~[?:?]
        at mineverse.Aust1n46.chat.utilities.Format.convertToJson(Format.java:110) ~[?:?]
        at mineverse.Aust1n46.chat.listeners.ChatListener.onAsyncPlayerChatEvent(ChatListener.java:690) ~[?:?]
        at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method) ~[?:1.8.0_191]
        at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62) ~[?:1.8.0_191]
        at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43) ~[?:1.8.0_191]
        at java.lang.reflect.Method.invoke(Method.java:498) ~[?:1.8.0_191]
        at org.bukkit.plugin.java.JavaPluginLoader$1.execute(JavaPluginLoader.java:302) ~[spigot-1.12.2.jar:git-Spigot-dcd1643-e60fc34]
        ... 11 more