[GEN][ZH] Fix undefined behavior in ThingTemplate::isEquivalentTo

[Caball009]

Another case of checking 'this' pointer in a member function like #870 & #878

GeneralsGameCode/GeneralsMD/Code/GameEngine/Source/Common/Thing/ThingTemplate.cpp

Lines 1479 to 1484 in 15a53d5

	Bool ThingTemplate::isEquivalentTo(const ThingTemplate* tt) const
	{
	// sanity
	if (!(this && tt))
	return false;

This pr fixes the undefined behavior in ThingTemplate::isEquivalentTo by making it a static function.

If the changes are considered acceptable, then it needs to be replicated in Generals. As far as I'm concerned that can be done in this pr as well.

[Mauller]

The better solution here might be to get rid of the equivalent to function and Instead implement an overload for the comparison operator within thingtemplate.

Then do (object->getTemplate() == otherTemplate)

[Caball009]

The better solution here might be to get rid of the equivalent to function and Instead implement an overload for the comparison operator within thingtemplate.

Then do (object->getTemplate() == otherTemplate)

I like that approach.

[xezon]

The change also needs to be replicated in Generals

[Caball009]

Updated and replicated in Generals.

I made the assumption that the ThingTemplate cannot be NULL for Objects and PartitionFilterThings. Afaik, objects are only created in ThingFactory::newObject, which checks if the template is NULL. I checked and all calls to PartitionFilterThings constructor are behind a template != NULL check. I added an assertion to the constructor for good measure.

[xezon]

Looks very safe.