Assertion failed: `running_process == nullptr` with maximum jitter

[wentasah]

When running demos as:

demos-sched -C 'windows: [{length: 2, sc_processes: [{cmd: sleep inf, budget: 1, jitter: 2}]}]'

it fails with

>>> 12:14:31.666 [critical] Assertion failed: `running_process == nullptr`
>>> 12:14:31.666 [critical]     at ../src/slice.cpp:39 (bool Slice::load_next_process(time_point))

Note that I triggered this while working on resolving #68. Current state of my work is in branch test. The most important change there is a testing framework that allows to test how demos schedules the processes. This means that it will be possible to add this test case to our test suite. I'd appreciate if @MatejKafka can look at what is causing this assertion failure before I do more changes to how demos schedules processes.

[wentasah]

Thanks.