Fixed mutliple bugs and BeatLeader compatibility.

[Hermanest]

This PR

• Fixes a problem of camera being subscribed to events even after destroy. The problem usually been happening in multiplayer.
• Fixes compatibility with BeatLeader in FPFC mode with Camera2 (when replayer camera is not available).
• Fixes compatibility with BeatLeader in just FPFC mode (when TrackedPoseDriver does not exist).

[nicoco007]

Thanks! I'll take a look at this as soon as I can.

[nicoco007]

Made some changes since the actual root cause is that it's subscribing the events twice when the game object is disabled during injection.