src: fix nullptr dereference for signal during startup
This fixes a test failure when running
test/parallel/test-child-process-spawnsync-kill-signal.js
under load. What would happen is that SignalExit()
tries
to shutdown the tracing agent, which might not have been set
up by the point that Node.js receives the signal.
Example failure: https://ci.nodejs.org/job/node-test-commit-linux-containered/4300/nodes=ubuntu1604_sharedlibs_zlib_x64/consoleFull
Checklist
-
make -j4 test
(UNIX), orvcbuild test
(Windows) passes -
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