src: fix inspector nullptr deref on abrupt exit

Fix a nullptr dereference on abrupt termination when async call stack
recording is enabled.

Bug discovered while trying to write a regression test for the bug fix
in commit df79b7d8 ("src: fix missing handlescope bug in inspector".)

PR-URL: https://github.com/nodejs/node/pull/17577


Reviewed-By: Anna Henningsen <anna@addaleax.net>
Reviewed-By: Timothy Gu <timothygu99@gmail.com>
Reviewed-By: Colin Ihrig <cjihrig@gmail.com>
Reviewed-By: Refael Ackermann <refack@gmail.com>
Reviewed-By: Eugene Ostroukhov <eostroukhov@google.com>