The newly introduced Effect panel, see https://gerrit.libreoffice.org/c/core/+/103835, crashes the application when expanding the panel. Happens in PanelLayout::GetOptimalSize() where m_xContainer is nil.
*** Bug 137696 has been marked as a duplicate of this bug. ***
andreas kainz committed a patch related to this issue.
It has been pushed to "master":
Resolves: tdf#137615 fix EffectPropertyPanel
It will be available in 7.1.0.
The patch should be included in the daily builds available at
https://dev-builds.libreoffice.org/daily/ in the next 24-48 hours. More
information about daily builds can be found at:
Affected users are encouraged to test the fix and report feedback.