Freeze break approval for gnome-software

[Richard Hughes <hughsient gmail com>]

Hi again,

Three commits I'd like to backport to 3.20:

Fixes a crash when double clicking on a .rpm/.deb/.xdg-app
https://git.gnome.org/browse/gnome-software/commit/?id=f6a9179f5b24d5bf59c478a925c6de95ab108611

Actually show an error dialog rather than just closing it automatically:
https://git.gnome.org/browse/gnome-software/commit/?id=a9431070cf980a58aa2e0a5e0b6ca9fa52d09187

Fixes visual glitch on Ubuntu when loading local files:
https://git.gnome.org/browse/gnome-software/commit/?id=8b74ae07b34e0bb1652b4d81e24eb4c1de68ac34

Happy to answer questions. Thanks.

Richard.