Crash on removing VST plugin filter (also when changing scene collection or exiting OBS)

Operating System Info

macOS 10.15

Other OS

No response

OBS Studio Version

27.0.0-rc6

OBS Studio Version (Other)

No response

OBS Studio Log URL

https://obsproject.com/logs/AE-o5-EAUZGByjwJ

OBS Studio Crash Log URL

https://www.dropbox.com/s/kbgps5z2neuz5iw/obs_crash.log?dl=0

Expected Behavior

When removing a VST plugin, or closing a scene collection with a VST plugin filter present on a source, for the plugin to be removed or scene collection to switch.

Current Behavior

OBS crashes to desktop whenever a VST plugin filter is removed.

Steps to Reproduce

1. Add a VST plugin filter to any audio source
2. Try to exit OBS or switch scene collection
3. Crash
   ...

Anything else we should know?

No problems occured on OBS v26, but problem was present on earlier v27 RC 4. VST plugin tested was TDR Kotelnikov: https://www.tokyodawn.net/tdr-kotelnikov/ (free).

My first attempt at writing up this report and the accompanying logs were for a crash when changing scene collections and/or exiting OBS entirely. I've now worked out it happens whenever my tested VST plugin is removed, which hopefully narrows the scope.

Start by reproducing the crash with the TDR Kotelnikov VST filter using the listed OBS log and crash log, then trace the filter-removal path exercised when removing the filter, switching scene collections, or exiting OBS. Done means the filter can be removed and scene collections or OBS can be closed without a crash on the reported macOS and OBS versions.