Unhandled Exception executing Command

I've been working on a plugin that gives users a certain item, in return for iron ingots. Basically the player types a command like:

/command amount

Now, whenever you leave the amount blank like: "/command" it gives me an internal server error. In the console it simply says:

"org.bukkit.command.CommandException: Unhandled exception executing command 'exchange' in plugin MyPlugin 0.1" along with some other mumbo-jumbo...

How do I fix this? I've tried doing something along the lines of:

Code:

            if (args[0] == null) {
                player.sendMessage("Type what color fool!");
                return true;
            }

But that doesn't help. Sorry if this is an extremely nooby question, but it's something that I want to learn how to fix :3

I'm using the CraftBukkit build (1000) by the way

Thanks

-8thDimension

 

Go here for help on making plugins.
http://forums.bukkit.org/forums/plugin-development.5/

 

Oohkie, sorry about that. I wasn't sure on which one to post on at first