Undo in Song Editor Fails After Duplicating Multiple Midi Reigions

Nobody has claimed this yet.

### Bug Summary
LMMS fails to to properly undo an operation where midi regions from two separate instrument tracks are duplicated.
This has also randomly caused crashes or instability.

#### Steps to reproduce
1. Create two instrument tracks next to each other in the song editor.
2. Create a Midi regions in each track and populate them with notes.
3. Select the multiple Midi regions simultaneously.
4. Use Ctrl+drag to duplicate the selected reigions to other positions in the tracks
5. Use Ctrl + Z to attempt an Undo

#### Expected behavior
The two duplicates are deleted.

#### Actual behavior
Only the duplicates in one of the instrument tracks are deleted.
A crash may occur depending on the instrument and project.

#### Screenshot

#### Affected LMMS versions
1.3.0 Alpha

#### Logs

Click to expand

Carla appears to be installed on this system at /usr/lib[64]/carla so we'll use it.

Jack appears to be installed on this system, so we'll use it.

Lv2 plugin SUMMARY: 95 of 192  loaded in 1550 msecs.

For details about not loaded plugins, please set

  environment variable "LMMS_LV2_DEBUG" to nonempty.

Lv2 Plugins blacklisted: 2 of 192 

  If you want to ignore the blacklist (dangerous!), please set

  environment variable "LMMS_IGNORE_BLACKLIST" to nonempty.

Start in the Song Editor flow for selecting and Ctrl-dragging multiple MIDI regions, then trace how Ctrl+Z handles duplicates across two instrument tracks. Reproduce the issue with two adjacent instrument tracks and verify that undo removes both duplicates without a crash or instability.

Written by the indexing model from the issue text.