Fix spinning bots, extract exceptions and constant firemode switching

[DrakiaXYZ]

• Nullguard all accesses to BotOwner.Mover, one of these was throwing an exception on extract so I just nullguarded everything
• Refactor the logic for checking if a bot is an enemy into a method, for easier re-use between GoalEnemy and LastEnemy checks
• Refactor check in AddEnemy to make sure the player isn't constantly removed from the bot's enemy list
• Verify that Person is set in a few places, to make sure we don't access invalid target data

[Solarint]

Added changes manually.