How to disable viewer

[pgimalac]

I have a simple question but I can't find the answer in the doc: how do I disable the viewer ?

I usually use zathura, but it doesn't give the focus back on sublime (I just want to build, see how it looks and keep writing...) even though I have "keep_focus": true, so I'd like to disable it, and just open zathura myself, which works well.

When I don't specify any viewer or give an empty command it just opens evince...