Fix mem-leak, Playlist/Region SessionHandleRef

When a playlist is deleted and drops_references(), any
undo/redo StatefulDiffCommand referncing playlist invoke
Destructible::drop_references() of the Command.

This leads to command_death(). As opposed to UndoTransaction::clear()
the StatefulDiffCommand was not destroyed.

In case of playlists StatefulDiffCommand::_changes contains
PBD::SequenceProperty<std::list<boost::shared_ptr<Region> > >
and shared pointer reference of the playlist regions were kept
indefinitely.

This fixes the following scenario:
New session, import an file, delete the created track,
clean up unused sources (delete unused playlists)[, quit].

A reference to the imported region was kept, because of the
playlist's undo command (insert region). Yet the source file
was deleted.


PS. Most playlist changes are accompanied by GUI zoom/selection
MementoCommands. Those are currently never directly dropped.
command_death() leaves those in place.

0 files changed, 0 insertions, 0 deletions