gnome3.gnome-shell: Fix screen recorder
gnome3.gnome-shell: Fix screen recorder

Trying to record screen (ctr-alt-shift-r) fails with the following logged:

	Can't create videoconvert element
	shell_recorder_close: assertion 'recorder->state != RECORDER_STATE_CLOSED' failed

videoconvert plug-in is part of gst-plugins-base.

NixOS/nixpkgs,NixOS/nixpkgs,NixOS/nixpkgs,NixOS/nixpkgs,NixOS/nixpkgs,NixOS/nixpkgs,NixOS/nixpkgs,NixOS/nixpkgs,NixOS/nixpkgs,NixOS/nixpkgs,NixOS/nixpkgs,NixOS/nixpkgs,NixOS/nixpkgs,NixOS/nixpkgs,NixOS/nixpkgs