Incorrect behavior of Ketcher after deleting of a part of R-Group member

[Svetlana-Asinovskaia]

Affected version: Release/2.2 + master
(standalone, remote)

Steps to reproduce:

1. Launch Ketcher
2. Draw a structure on the canvas, e.g. benzene
3. Draw another structure, e.g. chain
4. Choose R-Group Fragment tool
5. Define the created structures as R-group R1 members
6. Select a part of benzene
7. Delete it in any way
8. Click 'Undo' button
9. Choose any template and click any R-group atom
10. Delete any R-group atom with 'Erase' tool

Expected result:
7. The selected part of benzene is deleted, R-Group definition and brackets are present on a canvas.
8. The deleted part of benzene is returned to a canvas.
9. It's possible to add any template to any R-group atom.
10. It's possible to delete any R-group atom with 'Erase' tool.

Actual result:
7. R-Group definition and brackets are deleted with the selected part of benzene.
8. It's not possible to return the deleted fragment on a canvas with 'Undo' button.
9. It's not possible to add any template to any R-group atom.
10. 'Erase' tool deletes the whole structure.

[Svetlana-Asinovskaia]

Release/2.2 Issue is closed as fixed