nirc crashes when user enters a command without arguments
nirc crashes when user enters a command without arguments

If you enter `/foo` (I tried `/clear`) the server crashes, here's the output:
```
/[...]/nirc/lib/irc.js:460
    if ( args[args.length-1].match(/\s/) ) {
                             ^
TypeError: Cannot call method 'match' of undefined
```
Checking for array length fixes this:
`if ( args.length > 0 && args[args.length-1].match(/\s/) ) {`
cjstewart88/nirc,cjstewart88/nirc