Castle doctrine (self-defense in your property law, lets say for non fancy pants people) only applies if you can prove without a reasonable doubt that the intruder is there to inflict harm on you or that you were in fear for threat of serious danger/fear for your life etc..
I doubt "while I was cleaning my shotgun I saw a drone flying over me and you know how much I love to shoot things so I aimed at it right away" holds up in court for castle doctrine. Not to mention it is not a common defense since whenever its used there is controversy..