[2.1.17] "Select new content for a blueprint" does not respect "Cancel"

[Dmytrozern]

Steps to reproduce:
1. Create a blueprint.
2. Open the blueprint from step 1 and click "Select new content for a blueprint" in the top left corner.
3. Select new entities.
4. Click "X" in the top right to cancel the blueprint update.

Expected behavior:
After step 4, BP should roll back to its state before step 2.

Actual behavior:
It saves the new state as If I would click "Save blueprint".

[Loewchen]

87343