[GEN][ZH] Fix crash upon beacon removal in GameLogic::logicMessageDispatcher

[Caball009]

• Fixes issue: Access violation in AsciiString constructor when placing a beacon #1063

GeneralsGameCode/GeneralsMD/Code/GameEngine/Source/GameLogic/System/GameLogicDispatch.cpp

Lines 1701 to 1716 in d92834c

	case GameMessage::MSG_REMOVE_BEACON:
	{
	AIGroup *allSelectedObjects = NULL;
	allSelectedObjects = TheAI->createGroup();
	thisPlayer->getCurrentSelectionAsAIGroup(allSelectedObjects); // need to act on all objects, so we can hide teammates' beacons.
	if( allSelectedObjects )
	{
	const VecObjectID& selectedObjects = allSelectedObjects->getAllIDs();
	for (VecObjectID::const_iterator it = selectedObjects.begin(); it != selectedObjects.end(); ++it)
	{
	Object *beacon = findObjectByID(*it);
	if (beacon)
	{
	const ThingTemplate *thing = TheThingFactory->findTemplate( beacon->getControllingPlayer()->getPlayerTemplate()->getBeaconTemplate() );
	if (thing->isEquivalentTo(beacon->getTemplate()))

There's no sanity check for beacon->getControllingPlayer()->getPlayerTemplate() which causes a crash if the template is a nullptr. I wasn't able to find out much about why this happens, though I did notice that the controlling player was marked as PLAYER_COMPUTER.

The game no longer crashes with this PR.

[xezon]

Looks similar to #972

So only getPlayerTemplate() needs null test, yes?

[Caball009]

Looks similar to #972

So only getPlayerTemplate() needs null test, yes?

Yes, that would be enough to fix this particular crash.

I won't pretend to have much insight which pointers can or cannot be nullptrs in this code base. Here's a place where they're also checked:

GeneralsGameCode/GeneralsMD/Code/GameEngine/Source/GameClient/GUI/ControlBar/ControlBar.cpp

Lines 1767 to 1772 in d92834c

	if (obj->getControllingPlayer()
	&& obj->getControllingPlayer()->getPlayerTemplate()
	&& obj->getControllingPlayer()->getPlayerTemplate()->getBeaconTemplate().compare(obj->getTemplate()->getName()) == 0
	)
	{

[Mauller]

This issue is likely similar to the AiCommand issue i had with Hackers.

In this instance the original player may have been deleted before the command is acted upon.

[Caball009]

This looks very similar to #987.

[xezon]

Can you try figure out the reason for the null template? Maybe there is something that needs to be fixed higher up.

Other than that, it would be good to only change what is necessary to fix this crash. If another pointer would cause crashing with a different repro, then that warrants another investigation independent of this one.