Created attachment 153019 [details]
document exhibiting described behaviour

This bug was filed from the crash reporting server and is br-1e34eff0-2703-4c29-bab5-8fc496e98468.
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Submitter note:  crashreport.libreoffice.org/stats/crash_details/138d3e62-7d90-47d2-af35-1ebc5d70c600, crashreport.libreoffice.org/stats/crash_details/91a01dd1-da54-48f6-a59b-b29b3d5cfede, crashreport.libreoffice.org/stats/crash_details/e9e500de-0e3e-40e9-808c-6f070157f886, and crashreport.libreoffice.org/stats/crash_details/9ec2e301-ce77-4ef6-9251-7f77fef0aa46 are for the same issue, same file. crashreport.libreoffice.org/stats/crash_details/3d7248e6-10ce-418b-9d1d-516ffc6c51aa is for the new file i started from empty. I.e., pretty reproducible for me. 


One-page document, saved to disk as docx, 30 lines 15 comments, with tracking of changes enabled, view checked for comments, and unchecked for track changes.

Steps to reproduce:
1. While editing text, delete a comment by deleting the text (or the triangular inline comment marker). Comment disappears from view
2. Use ctrl-z to try to undo the deletion of the comment
3. Writer freezes or crashes 80-90% of time on each attempt; if it does not on first try, repeat steps 1 and 2 (so far for me, always by third attempt) .
4. I can reopen the document, repeat the steps 1 and 2, and the behaviour recurs 
5. I can create a new file with nonsense, add 12 comments, save as docx and the behaviour will appear
6. Same file saved as odt did not exhibit this behaviour

Actual results: Crash or program freeze requiring forcing close
Expected results: Undo of deleted comment