Carlos Garnacho authored Apr 26, 2019 and Florian Müllner committed Apr 27, 2019

On one hand, we were using a path instead of an URI on
rsvg_handle_set_base_uri(). This broke at some point in librsvg
(presumably for the best, handling paths there sounds non-standard)
leaving a blank svg (As the base image wouldn't be accessed).

On the other hand, we use this with the deprecated rsvg_handle_write()
which we should drift away from.

Using rsvg_handle_new_from_stream_sync() neatly solves both. We use
newer API based on input streams and GFiles, and it internally does
the right thing, bringing the pad OSD back to life.

Closes: #1220