Crash when copying audio TCOs between LMMSs.

[husamalhomsi]

Using Windows 10 Pro, 64-bit OS, x64-based processor with LMMS 1.2.0-rc.4.

To reproduce:

1. Open 2 LMMSs.
2. In each LMMS, add either a sample track or an AFP.
3. Add a TCO with info (not an empty sample track or AFP) to the track of a LMMS.
4. Control and drag the TCO from one LMMS's track to the other to make a copy.

Once the copied TCO enters the track, LMMS will crash, the runtime error window will appear,

then the "LMMS has stopped working" window will appear.

[musikBear]

Could not recreate exactly on win32. rc4 xp3
However, for** AFP **the actual TCO is stripped and only the instrument is copied to 2. instance of LMMS
Copying a 3oc track with TCO went perfect
Copying a sample-track track with TCO went perfect

[PhysSong]

Reproduced. It seems like TrackContentWidget::canPasteSelection assumes the source track is from the same instance of LMMS:

lmms/src/core/Track.cpp

Lines 1382 to 1394 in daa3f53

	// Track must be in TrackContainer's tracks
	if( finalTrackIndex < 0 || finalTrackIndex >= tracks.size() )
	{
	return false;
	}
	// Track must be of the same type
	Track * startTrack = tracks.at( trackIndex );
	Track * endTrack = tracks.at( finalTrackIndex );
	if( startTrack->type() != endTrack->type() )
	{
	return false;
	}

I guess saving track type in createTCODataFiles and using it in canPasteSelection will be enough.

[PhysSong]

Note that the crash only happens if a track whose index equals to the index of source track doesn't exist in target LMMS instance.

[PhysSong]

Should be fixed in #4862.