Use of deleted Adaptor in formatContextFinalizer()

[mandersan]

Hi,

I've seen a number of odd issues when using Beamcoder heavily, and I believe this is due to a 'use after free' issue in the following line of code - https://github.com/Streampunk/beamcoder/blob/master/src/format.cc#L3831

Immediately prior to this the Governor is collected which deletes the Adaptor instance, so the Adaptor instance (passed as a hint) used in formatContextFinalizer() is no longer valid.

The issues I've seen are segfaults & hangs (waiting to lock an invalid mutex), and stability is much better removing the above mentioned call to 'adaptor->finish()'.

I'm not sure that this is the best fix for this issue though, which is why I've not submitted a pull request.

Thanks

[scriptorian]

Thanks very much for the report!
I have reviewed this and made the change you suggested, along with a few other tidy ups.