How to create blank audio file in FFMPEG?

Question

I am creating a project associated with using Sony ILCE-6000 with its remotely controlled functions.

I have found such method of controlling camera with command line: https://github.com/tonytonyjan/sonycam

There is also a part about streaming. I try using the code which I found there:

$ sonycam liveview | ffmpeg -f image2pipe  -c mjpeg -i pipe:0 -codec copy http://127.0.0.1:8080/feed1.ffm

But what I get is:

Missing audio stream which is required by this ffm

Anyone knows a solution?