Passing nil as argument to Emit causes panic.

[muja]

reflect package panics if you make a call with nil argument. You have to explicitly cast it first...
Here is some minor discussion about it:
https://groups.google.com/forum/#!topic/golang-nuts/apNcACpl_fI

I'm using it for error passing, and if error is nil, the function panics!

panic: reflect: Call using zero Value argument

goroutine 37 [running]:
reflect.Value.call(0x4dcde0, 0xc20801f820, 0x13, 0x600ca0, 0x4, 0xc20809ec00, 0x2, 0x2, 0x0, 0x0, ...)
    /go/1.4.2/libexec/src/reflect/value.go:360 +0x491
reflect.Value.Call(0x4dcde0, 0xc20801f820, 0x13, 0xc20809ec00, 0x2, 0x2, 0x0, 0x0, 0x0)
    /go/1.4.2/libexec/src/reflect/value.go:296 +0xbc
github.com/chuckpreslar/emission.func·003(0x4dcde0, 0xc20801f820, 0x13)
    /github.com/chuckpreslar/emission/emitter.go:198 +0x16a
created by github.com/chuckpreslar/emission.(*Emitter).Emit
    /github.com/chuckpreslar/emission/emitter.go:199 +0x5c5