Kill a sequence of delays: crash with "Internal error"

Describe the bug
Killing a sequence of delays can make Batsim crash with an "Internal error"

Provide information so the bug can be reproduced

• Grab a copy of Batsim 19b6386b (framagit, pytest branch)
• Replace pytest.xfail("something seems wrong with sequences") by pass in ./test/test_kill.py.
• Run nix-build ./release.nix -A integration_tests
• Two tests from test_kill.py should fail as expected. Test report can be opened with firefox ./result/pytest_report.html

Logs

...
[master_host:Scheduler REQ-REP:(4) 0.000045] [network/INFO] Received '{"now":10.000045,"events":[{"timestamp":0.000045,"type":"EXECUTE_JOB","data":{"job_id":"d3e758!1","alloc":"0"}},{"timestamp":10.000045,"type":"KILL_JOB","data":{"job_ids":["d3e758!1"]}}]}'
[Bourassa:job_d3e758!1:(5) 0.000060] [jobs_execution/INFO] Sleeping the whole task length
[Bourassa:job_d3e758!1:(5) 10.000060] [jobs_execution/INFO] Sleeping done
[Bourassa:job_d3e758!1:(5) 10.000060] [jobs_execution/INFO] Sleeping the whole task length
[master_host:killer_process:(6) 10.000060] /tmp/nix-build-batsim-3.0.0.drv-2/batsim/src/jobs.cpp:136: [root/CRITICAL] Internal error
(backtrace not set -- did you install Boost.Stacktrace?)
/home/carni/proj/batsim/test/test-out/kill-after10s-killer-small-delaysequences-noredis/cmd/batsim.bash: line 1: 15623 Aborted                 (core dumped) batsim -p '/home/carni/proj/batsim/platforms/small_platform.xml' -w '/home/carni/proj/batsim/workloads/test_sequence_delay.json' -e '/home/carni/proj/batsim/test/test-out/kill-after10s-killer-small-delaysequences-noredis/batres' --forward-profiles-on-submission

pytest.log