Large Aero Crit View Bug Fixes

[SJuliez]

In the Large Aero Crit View:

• No longer throws exceptions when dragging an "--Empty--" slot
• No longer sometimes adds duplicate equipment when using the Copy from other side buttons
• Weapons dragged from one location to another will no longer sometimes not disappear from the source arc

I thought I would need removeEmptyBays() as a utility at another class but in the end I didnt. It still seemed like a valid change to move this method to the UnitUtils so I left it in.