Calling Write() with no output throws an exception

[kamsar]

To reproduce:

• Implement a basic cmdlet (or hack one that already exists)
• As the first statement in its implementation call Host.UI.Write("anything")
• Call the cmdlet

An out of range exception is thrown, due to the array count check here becoming index -1 if the Output has nothing in it yet.

Edge case? Yes. And it was because I was using it wrong anyway ;)

[AdamNaj]

Still, worth fixing, some people make this call from their scripts.
Fixed.