torrc-defaults gets overwritten during update

After updating Tor Browser from 5.0.4 to 5.0.5 recently I noticed that my settings in torrc-defaults have all gone and now I have a fresh config file. While I understand why keeping old config with new software might not be the best way of working, I think it's good to have this file automatically backed up with name like torrc-defaults.orig.1 or similar. May be even give a note on this to user after successful update. Marked its severity as Major because user can lose all his settings and stay unnoticed until she checks this file later.

Trac:
Username: Unchqua