PermissionsEx - "an internal problem has occurred"

Hey everyone,
I've been trying for ages to fix this is issue. Everytime I type /pex into chat it tells me "an internal error occurred while attempting to perform this command." I still haven't been able to fix it, so I'm taking to the forums now. I've searched through countless forums and tried everything. Nothing has worked.

I looked into the console to see what comes up when I type in /pex.
Here it is:
[21:09:43] [Server thread/WARN]: Unexpected exception while parsing console command "pex user arcticbots group add admin"
org.bukkit.command.CommandException: Unhandled exception executing command 'pex' in plugin PermissionsEx v1.14
at org.bukkit.command.PluginCommand.execute(PluginCommand.java:47) ~[craftbukkit.jar:git-Bukkit-5193f76]
at org.bukkit.command.SimpleCommandMap.dispatch(SimpleCommandMap.java:148) ~[craftbukkit.jar:git-Bukkit-5193f76]
at org.bukkit.craftbukkit.v1_14_R1.CraftServer.dispatchCommand(CraftServer.java:686) ~[craftbukkit.jar:git-Bukkit-5193f76]
at org.bukkit.craftbukkit.v1_14_R1.CraftServer.dispatchServerCommand(CraftServer.java:672) [craftbukkit.jar:git-Bukkit-5193f76]
at net.minecraft.server.v1_14_R1.DedicatedServer.handleCommandQueue(DedicatedServer.java:406) [craftbukkit.jar:git-Bukkit-5193f76]
at net.minecraft.server.v1_14_R1.DedicatedServer.b(DedicatedServer.java:371) [craftbukkit.jar:git-Bukkit-5193f76]
at net.minecraft.server.v1_14_R1.MinecraftServer.a(MinecraftServer.java:909) [craftbukkit.jar:git-Bukkit-5193f76]
at net.minecraft.server.v1_14_R1.MinecraftServer.run(MinecraftServer.java:763) [craftbukkit.jar:git-Bukkit-5193f76]
at java.lang.Thread.run(Unknown Source) [?:1.8.0_231]
Caused by: java.lang.NullPointerException
at ru.tehkode.permissions.bukkit.PermissionsEx.onCommand(PermissionsEx.java:123) ~[?:?]
at org.bukkit.command.PluginCommand.execute(PluginCommand.java:45) ~[craftbukkit.jar:git-Bukkit-5193f76]
... 8 more
hope somebody can reply as soon as possible!