Description of the Change

When a task callback returns, it looks like RTOS deletes the task. Therefore, when a CrossplatformThread is destructed, and the task callback has already returned, it is deleting an already deleted task. This causes a segfault.

Motivation

Segfaults are bad, though I think this situation is fairly rare: a short-lived task being held by a CrossPlatformThread that will be destructed before program end.

Possible Drawbacks

It's possible that STATE_INVALID might also need to be checked on, but I don't think so.

Verification Process

This causes the unit tests in my own code to pass and not segfault. This is only reproducible on the V5 brain, std::threads behave better when double deleted (or they aren't deleted when the callback ends).

Otherwise my code works fine and CrossplatformThread still works.

Example

This segfaults:

void initialize() {
        CrossplatformThread c([](void*){std::cout << "i am a fickle task" << std::endl;}, nullptr);
        pros::delay(500);
}