#112 Output file not released on failure

[Joe Smith]

After getting a "demux: Failed to close gop - choose
another frame for your cut" error, I tried to view the
truncated output file in an MPEG player to determine
which cut caused the problem. I could not because the
file was still open by TyEditor.

Fix: close the output file when processing stops, for
both successful and unsuccessful cases.

As is stands now, I have to save the marker file, exit
completely from TyStudio, play the mpeg to its end,
restart TyStudio, re-open *.ty file, load cuts back in.