allow tor to start if torrc does not exist
For TBB 3.x, we now put all of the default settings in a torrc-defaults file. The torrc file within the Tor data directory will be reserved for the user's custom settings. The goal is to not overwrite the user's settings when they (or our future automatic updater) overlays a new version of TBB on top of an existing installation, while still providing a way to include default settings.
But tor will not start up if the -f command line option points to a torrc file that does not exist. Here is a proposal: if a torrc-defaults file is provided, do not require that torrc exist. If this is too difficult to implement or distasteful in some way, we could probably instead modify the programs and scripts that start the TBB browser to create an empty torrc before starting anything. That would be a little more fragile though.