Cannot create ipc server socket file

Hi.

I'm trying to use celluloid with the option `input-ipc-server=/tmp/gmpv-socket` and `idle=yes`, but the socket file that is supposed to be created at /tmp/gmpv-socket it's not there.

I tried this with the non-flatpak version of celluloid and, even simply using `--idle --input-ipc-server=/tmp/gmpv-socket`, in the "mpv extra options, creates the file immediately when saving.

So, this is probably a bug in the flatpak version.