Unhandled exception executing tab-completer

[dwesolowski]

When using tab-completer if I space after the last <arg> when entering a command I get the error below.

Unhandled exception executing tab-completer

public List<String> getSubcommandArguments(Player player, String[] args) {
        if (args.length == 2) {
            return Arrays.asList("<player>")
        }
        return null;
    }

The only way I could resolve this was to remove the @NotNull after public below in CoreCommand.java

public List<String> tabComplete(@NotNull CommandSender sender