Toggling permissions.memory_only causes crash of Tor Browser

While investigating #9531 (moved) I run into an other reason for crashing when hitting New Identity:

WARNING: NS_ENSURE_TRUE(asyncCloseWasCalled) failed: file /home/firefox/tor-browser/storage/src/mozStorageConnection.cpp, line 943
Assertion failure: !mAsyncExecutionThread, at /home/firefox/tor-browser/storage/src/mozStorageConnection.cpp:415

Program ./Browser/firefox (pid = 30485) received signal 11.

Commenting out the code toggling "permissions.memory_only" seems to help.

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