Use a sturdier headless check

[BlueCyro]

I noticed that a type check was being used, whereas checking the provided SystemInfo class should be more future-proof if something changes.

[BlueCyro]

Hold up, made an oopsie

[BlueCyro]

There we are, StandaloneSystemInfo should avoid the headless reference before we check if we're on a headless.

[badhaloninja]

StandaloneSystemInfo will always return Headless, it's the headless specific ISystemInfo class This could be properly implemented here by checking Engine.SystemInfo after "on engine init" but I won't be doing that right now