[OSX] Threading is broken for multi-import menu actions

[meanmedianmoge]

Describe the bug
The application crashes upon selecting either Import Multiples or Import as a Version from the File menu. This can be circumvented be re-routing the menu action directly to the import backend. However, we'd like to retain the threading so it is functionally equivalent to SD multi-imports.

To Reproduce
Steps to reproduce the behavior:

1. Open the Librarian
2. Click on File > Import Multiple
3. The application will crash
4. See error

Expected behavior
Expected the threading to initialize properly and for non-SD patches to be imported correctly.

Desktop (please complete the following information):

• Mac OSX 10.15.4

Additional context
Solved by removing the thread connection to the menu-actions. Use the current SD-related threading to debug behavior.

[meanmedianmoge]

Putting in the temporary fix for now, such that menu action multi-imports are not threaded. Will move this over to the next project following the 1.0 release.