Cleanup more the entities once they get destructed

[necessarily-equal]

Supposedly fixes Unvanquished/Unvanquished#1939

[necessarily-equal]

I tried to use the arrays EmptyEntity::componentOffsets and EmptyEntity::messageHandlers instead, but they are apprently private. This PR is an alternative solution.

/home/afontain/unv/Unvanquished/src/sgame/backend/CBSEBackend.cpp: In destructor ‘virtual Entity::~Entity()’:
/home/afontain/unv/Unvanquished/src/sgame/backend/CBSEBackend.cpp:24:41: error: ‘const int EmptyEntity::componentOffsets []’ is private within this context
   24 |         componentOffsets = EmptyEntity::componentOffsets;
      |                                         ^~~~~~~~~~~~~~~~
In file included from /home/afontain/unv/Unvanquished/src/sgame/backend/CBSEBackend.cpp:9:
/home/afontain/unv/Unvanquished/src/sgame/backend/CBSEEntities.h:37:34: note: declared private here
   37 |                 static const int componentOffsets[];
      |                                  ^~~~~~~~~~~~~~~~
/home/afontain/unv/Unvanquished/src/sgame/backend/CBSEBackend.cpp:25:40: error: ‘void (* const EmptyEntity::messageHandlers [])(Entity*, const void*)’ is private within this context
   25 |         messageHandlers = EmptyEntity::messageHandlers;
      |                                        ^~~~~~~~~~~~~~~
In file included from /home/afontain/unv/Unvanquished/src/sgame/backend/CBSEBackend.cpp:9:
/home/afontain/unv/Unvanquished/src/sgame/backend/CBSEEntities.h:34:45: note: declared private here
   34 |                 static const MessageHandler messageHandlers[];
      |                                             ^~~~~~~~~~~~~~~
[54/55] Building CXX object CMakeFiles/s...c/sgame/components/TurretComponent.cpp.o
ninja: build stopped: subcommand failed.
ninja -C build-nixos  236.92s user 13.48s system 373% cpu 1:07.06 total

[DolceTriade]

Can you explain the bug in detail so we can learn?

[slipher]

Is your hypothesis that one of the components of the entity being destroyed tries to access one of the entity's other components from its destructor? If that's the case, the fix won't help as ~Entity() only runs after all of the component destructors run.

[slipher]

Is your hypothesis that one of the components of the entity being destroyed tries to access one of the entity's other components from its destructor?

Well that's not it - the only two components with user-defined destructors are TurretComponent and SpawnerComponent. (The latter does have something of a bug of the type I described though - Unvanquished#2233)

[necessarily-equal]

Marking as draft before I find time to test more (probably not soon)

[illwieckz]

It looks like this submodule reference had been mistakenly committed.

I noticed it because a sync submodules commit reverted it:

• Unvanquished/Unvanquished@681fb35

[illwieckz]

It looks to have been committed in Unvanquished/Unvanquished@4fb94c2