Gracefully fallback to default if given `sinkId` or `deviceId` does not exists

[b-ma]

Not sure how we want these to behave, to be discussed:

For output selection (AudioContext and sinkId), if the required sinkId is wrong, we get the following error message NotFoundError: invalid sinkId "coucou"

For input selection (getUserMedia and deviceId), if the required deviceId is wrong we have the following, and quite cryptic, error message: called Option::unwrap() on a None value

In both cases, it seems that Chrome and Firefox fallback to default device (Chrome additionally add a log in the console)

[orottier]

Logging and using a default seems sane to me. I can build that