Hotfix r2498

[h2]Changelog[/h2]

• Fixed Blackhole's NullReferenceException error when it (somehow) gets something that isn't an enemy.
  
• Fixed Bubble Bullets trying to kill its bubble tracker animation which might already be deleted.
  
• Fixed Burst Laser's charged bullet firing breaking when firing a charged shot pattern.
  
• Fixed Null Value exception in bullet physics.
  
• Bullet Opacity is now applied correctly on restart.