fix issue with style argument for outputs

[morsecodist]

For some reason on my setup I can't produce outputs at all. I am getting an error that style should be a String rather than nil. I will be honest I don't have a deep understanding of why this is or why it specifically happens on my system. However, this slight change to the way the arguments are constructed fixes the problem in a way that should be compatible. I also personally find it a little more readable.

[benlubas]

@morsecodist what version of python, pynvim, and neovim are you running when you get that error?

Never mind, reproduced. If I had to guess pynvim changed something and now the old way breaks

[hhhhhhh2019]

This error occurs because neovim currently only supports the "minimal" style(None also not supported)