I need Help fixing an error with SafePet

Hello, My name Is Treecko5551Plays and I have a server that I play with my friends on. My friends and I wanted access to unsit our pet wolves and so I went onto PloudOS.com where I turn off and on the server and installed the "SafePet" Plugin. The Plugin allows for us to give our dogs Ids and assign new owners but there's another command that I everytime I try to type it in it says "An internal error occurred while attempting to preform this command. And I don't know what's wrong. I'll post the log.

[17:50:30 INFO]: Treecko5551Plays issued server command: /safepet members add 028 Treecko5551Plays
[17:50:30 ERROR]: null>
org.bukkit.command.CommandException: Unhandled exception executing command 'safepet' in plugin SafePet v1.2.6
at org.bukkit.command.PluginCommand.execute(PluginCommand.java:47) ~[server.jar:git-Paper-414]
at org.bukkit.command.SimpleCommandMap.dispatch(SimpleCommandMap.java:159) ~[server.jar:git-Paper-414]
at org.bukkit.craftbukkit.v1_16_R3.CraftServer.dispatchCommand(CraftServer.java:807) ~[server.jar:git-Paper-414]
at net.minecraft.server.v1_16_R3.PlayerConnection.handleCommand(PlayerConnection.java:2021) ~[server.jar:git-Paper-414]
at net.minecraft.server.v1_16_R3.PlayerConnection.c(PlayerConnection.java:1832) ~[server.jar:git-Paper-414]
at net.minecraft.server.v1_16_R3.PlayerConnection.a(PlayerConnection.java:1785) ~[server.jar:git-Paper-414]
at net.minecraft.server.v1_16_R3.PacketPlayInChat.a(PacketPlayInChat.java:47) ~[server.jar:git-Paper-414]
at net.minecraft.server.v1_16_R3.PacketPlayInChat.a(PacketPlayInChat.java:5) ~[server.jar:git-Paper-414]
at net.minecraft.server.v1_16_R3.PlayerConnectionUtils.lambda$ensureMainThread$1(PlayerConnectionUtils.java:23) ~[server.jar:git-Paper-414]
at net.minecraft.server.v1_16_R3.TickTask.run(SourceFile:18) ~[server.jar:git-Paper-414]
at net.minecraft.server.v1_16_R3.IAsyncTaskHandler.executeTask(IAsyncTaskHandler.java:136) ~[server.jar:git-Paper-414]
at net.minecraft.server.v1_16_R3.IAsyncTaskHandlerReentrant.executeTask(SourceFile:23) ~[server.jar:git-Paper-414]
at net.minecraft.server.v1_16_R3.IAsyncTaskHandler.executeNext(IAsyncTaskHandler.java:109) ~[server.jar:git-Paper-414]
at net.minecraft.server.v1_16_R3.MinecraftServer.bb(MinecraftServer.java:1132) ~[server.jar:git-Paper-414]
at net.minecraft.server.v1_16_R3.MinecraftServer.executeNext(MinecraftServer.java:1125) ~[server.jar:git-Paper-414]
at net.minecraft.server.v1_16_R3.IAsyncTaskHandler.awaitTasks(IAsyncTaskHandler.java:119) ~[server.jar:git-Paper-414]
at net.minecraft.server.v1_16_R3.MinecraftServer.sleepForTick(MinecraftServer.java:1086) ~[server.jar:git-Paper-414]
at net.minecraft.server.v1_16_R3.MinecraftServer.w(MinecraftServer.java:1000) ~[server.jar:git-Paper-414]
at net.minecraft.server.v1_16_R3.MinecraftServer.lambda$a$0(MinecraftServer.java:173) ~[server.jar:git-Paper-414]
at java.lang.Thread.run(Thread.java:748) [?:1.8.0_212]
Caused by: java.lang.ClassCastException: org.bukkit.configuration.MemorySection cannot be cast to java.util.Collection
at tk.jgsbroadcast.safepet.command.cmds.MemberCommand.onCommand(MemberCommand.java:45) ~[?:?]
at tk.jgsbroadcast.safepet.managers.CommandManager.onCommand(CommandManager.java:100) ~[?:?]
at org.bukkit.command.PluginCommand.execute(PluginCommand.java:45) ~[server.jar:git-Paper-414]
... 19 more