This bug is for crash report bp-e4c7a610-1076-4303-b9c2-e612e0190616.

Top 10 frames of crashing thread:

0 xul.dll PLDHashTable::Search xpcom/ds/PLDHashTable.cpp:510
1 xul.dll mozilla::dom::quota::QuotaObject::Release dom/quota/ActorsParent.cpp:2763
2 xul.dll void mozilla::dom::`anonymous namespace'::Datastore::ConnectionClosedCallback dom/localstorage/ActorsParent.cpp:5458
3 xul.dll nsresult mozilla::detail::RunnableMethodImpl< xpcom/threads/nsThreadUtils.h:1176
4 xul.dll void mozilla::dom::`anonymous namespace'::Connection::CloseOp::Cleanup dom/localstorage/ActorsParent.cpp:4680
5 xul.dll nsresult mozilla::dom::`anonymous namespace'::ConnectionDatastoreOperationBase::Run dom/localstorage/ActorsParent.cpp:4090
6 xul.dll nsThread::ProcessNextEvent xpcom/threads/nsThread.cpp:1215
7 xul.dll NS_ProcessNextEvent xpcom/threads/nsThreadUtils.cpp:486
8 xul.dll mozilla::ipc::MessagePumpForNonMainThreads::Run ipc/glue/MessagePump.cpp:333
9 xul.dll MessageLoop::RunHandler ipc/chromium/src/base/message_loop.cc:308

Maybe it's also the group mismatching issue.

Well, this is the case when the object is being released, not created.

The last build I see crashes for is 73.0b4 from Nov. 22. Any thoughts what might have fixed this?

Edit: seems I confused something, ignore this.

73.0b5 was released just yesterday, I think it's too early to say this bug has been fixed.
73.0b4 was released on 13-Jan-2020.

Perhaps not gone, but certainly greatly reduced in frequency since early November https://crash-stats.mozilla.org/signature/?signature=PLDHashTable%3A%3ASearch%20%7C%20mozilla%3A%3Adom%3A%3Aquota%3A%3AQuotaObject%3A%3ARelease&date=%3E%3D2019-08-21T03%3A45%3A00.000Z&date=%3C2020-02-21T03%3A45%3A00.000Z#graphs

in fact, there are no crash reports in the past six months for any current version. Version 60 are The only crashes reported.