I was testing Spigot 1.10 and decided to OP myself from the console. I didn't press the p hard enough and it wasn't typed. Anyway I then left a space and pressed tab to automatically type my name, but because /o isn't a command, the console spewed out this error:

[17:50:08] [Server console handler/WARN]: Unhandled exception when tab completing
java.util.concurrent.ExecutionException: java.lang.IllegalArgumentException: completions
at org.bukkit.craftbukkit.v1_10_R1.util.Waitable.get(Waitable.java:42) ~[Spigot-1.10.jar:git-Spigot-da278d1-b2f31b7]
at org.bukkit.craftbukkit.v1_10_R1.command.ConsoleCommandCompleter.complete(ConsoleCommandCompleter.java:35) [Spigot-1.10.jar:git-Spigot-da278d1-b2f31b7]
at org.bukkit.craftbukkit.libs.jline.console.ConsoleReader.complete(ConsoleReader.java:3261) [Spigot-1.10.jar:git-Spigot-da278d1-b2f31b7]
at org.bukkit.craftbukkit.libs.jline.console.ConsoleReader.readLine(ConsoleReader.java:2621) [Spigot-1.10.jar:git-Spigot-da278d1-b2f31b7]
at net.minecraft.server.v1_10_R1.DedicatedServer$2.run(DedicatedServer.java:83) [Spigot-1.10.jar:git-Spigot-da278d1-b2f31b7]
Caused by: java.lang.IllegalArgumentException: completions
at org.apache.commons.lang.Validate.notNull(Validate.java:192) ~[Spigot-1.10.jar:git-Spigot-da278d1-b2f31b7]
at org.bukkit.event.server.TabCompleteEvent.<init>(TabCompleteEvent.java:26) ~[Spigot-1.10.jar:git-Spigot-da278d1-b2f31b7]
at org.bukkit.craftbukkit.v1_10_R1.command.ConsoleCommandCompleter$1.evaluate(ConsoleCommandCompleter.java:27) ~[Spigot-1.10.jar:git-Spigot-da278d1-b2f31b7]
at org.bukkit.craftbukkit.v1_10_R1.command.ConsoleCommandCompleter$1.evaluate(ConsoleCommandCompleter.java:1) ~[Spigot-1.10.jar:git-Spigot-da278d1-b2f31b7]
at org.bukkit.craftbukkit.v1_10_R1.util.Waitable.run(Waitable.java:24) ~[Spigot-1.10.jar:git-Spigot-da278d1-b2f31b7]
at net.minecraft.server.v1_10_R1.MinecraftServer.D(MinecraftServer.java:747) ~[Spigot-1.10.jar:git-Spigot-da278d1-b2f31b7]
at net.minecraft.server.v1_10_R1.DedicatedServer.D(DedicatedServer.java:399) ~[Spigot-1.10.jar:git-Spigot-da278d1-b2f31b7]
at net.minecraft.server.v1_10_R1.MinecraftServer.C(MinecraftServer.java:672) ~[Spigot-1.10.jar:git-Spigot-da278d1-b2f31b7]
at net.minecraft.server.v1_10_R1.MinecraftServer.run(MinecraftServer.java:571) ~[Spigot-1.10.jar:git-Spigot-da278d1-b2f31b7]
at java.lang.Thread.run(Unknown Source) ~[?:1.8.0_66]

Here's the whole console log: http://pastebin.com/xhhA5q3Q