[11:02:58] [Server thread/ERROR]: #!#! Stack trace:
[11:02:58] [Server thread/ERROR]: #!#! java.lang.UnsupportedOperationException
[11:02:58] [Server thread/ERROR]: #!#!     at ch.njol.skript.lang.ExpressionList.getSingle(ExpressionList.java:87)
[11:02:58] [Server thread/ERROR]: #!#!     at ch.njol.skript.expressions.ExprTarget.init(ExprTarget.java:69)
[11:02:58] [Server thread/ERROR]: #!#!     at ch.njol.skript.lang.SkriptParser.parse(SkriptParser.java:251)
[11:02:58] [Server thread/ERROR]: #!#!     at ch.njol.skript.lang.SkriptParser.parse(SkriptParser.java:178)
[11:02:58] [Server thread/ERROR]: #!#!     at ch.njol.skript.lang.SkriptParser.parseSingleExpr(SkriptParser.java:323)
[11:02:58] [Server thread/ERROR]: #!#!     at ch.njol.skript.lang.SkriptParser.parseExpression(SkriptParser.java:623)
[11:02:58] [Server thread/ERROR]: #!#!     at ch.njol.skript.lang.SkriptParser.parseFunction(SkriptParser.java:1100)
[11:02:58] [Server thread/ERROR]: #!#!     at ch.njol.skript.lang.function.EffFunctionCall.parse(EffFunctionCall.java:45)
[11:02:58] [Server thread/ERROR]: #!#!     at ch.njol.skript.lang.Effect.parse(Effect.java:61)
[11:02:58] [Server thread/ERROR]: #!#!     at ch.njol.skript.command.Commands.handleEffectCommand(Commands.java:285)
[11:02:58] [Server thread/ERROR]: #!#!     at ch.njol.skript.command.Commands$4$1.call(Commands.java:228)
[11:02:58] [Server thread/ERROR]: #!#!     at ch.njol.skript.command.Commands$4$1.call(Commands.java:1)
[11:02:58] [Server thread/ERROR]: #!#!     at org.bukkit.craftbukkit.v1_12_R1.scheduler.CraftFuture.run(CraftFuture.java:85)
[11:02:58] [Server thread/ERROR]: #!#!     at org.bukkit.craftbukkit.v1_12_R1.scheduler.CraftScheduler.mainThreadHeartbeat(CraftScheduler.java:415)
[11:02:58] [Server thread/ERROR]: #!#!     at net.minecraft.server.v1_12_R1.MinecraftServer.D(MinecraftServer.java:833)
[11:02:58] [Server thread/ERROR]: #!#!     at net.minecraft.server.v1_12_R1.DedicatedServer.D(DedicatedServer.java:426)
[11:02:58] [Server thread/ERROR]: #!#!     at net.minecraft.server.v1_12_R1.MinecraftServer.C(MinecraftServer.java:767)
[11:02:58] [Server thread/ERROR]: #!#!     at net.minecraft.server.v1_12_R1.MinecraftServer.run(MinecraftServer.java:665)
[11:02:58] [Server thread/ERROR]: #!#!     at java.lang.Thread.run(Thread.java:748)