Fix isFeatureCameraActive for Spectator enhacements

[Fusselwurm]

At the moment, isFeatureCameraActive does not detect ACE spectator mode, because ace_spectator_camera as a variable was removed in 77c2b99 .
spectator module initializes three separate cameras instead, of which for example ace_spectator_freeCamera could be used to check if spec mode is active.

[kymckay]

This could be changed to check EGVAR(spectator,isSet) as it will also support the overhaul once it is merged for 3.11, but otherwise 👍

[jonpas]

Let's do what @SilentSpike said, and we can merge. missionNamespace getVariable [nil, objNull] will return objNull btw? If not, we need to make sure that function still works if spectator is not present (as in removed PBO).

[kymckay]

@jonpas Isn't that the whole point of the second getVariable argument? 😆

Also note that isSet is a boolean, just to clarify. Will be true when spectator is open.

[jonpas]

Uh, I could bet I wanted to write something else there after writing the rest... but I forgot now.