Steps to reproduce:
1. Open attached project DDLC_Engine (OC link)
2. Open Scene "Testing"
3. Select Natsuki-Chibi (under Canvas->Poem Writing->Stickers) in the Hierarchy
4. Open Window->Animation with Natsuki-Chibi selected
5. Move to any frame in between the two keyframes on the timeline
6. Delete Natsuki-Chibi (try steps 5-6 a few times, it tends to crash after a few attempts)

Note: Check the attached video to see it in action
Note 2: this crash reproduces sometimes, but not always. That should not depend on any changes made to the scene since it was tested with the same setup every time

Reproduced with: 2017.1.0a1, 2017.1.1f1, 2017.3.0f3, 2018.1.0a7
Not reproduced with: 5.6.0f3, 5.6.4f1