app: Fix Gst.init parameters
Created by: RyuzakiKK
Gst.init() requires a [str] or None as parameters.
On ArchLinux with the package gst-python that is "GStreamer Python
binding overrides (complementing the bindings provided by python-gi)",
leaving init() without parameters causes a runtime error.
Adding None
as parameter it will works with gst-python and also
without it.