Trick or treating: seriously scared

I live on my own now because I have recently moved into a flat. I am very worried about the prospect of pesky trick or treaters (complete strangers) knocking on my door on the 31st. Of course I would not answer. I never answer the door to strangers/cold callers. But would they then do a nasty criminal prank? Like throw egg at my flat or set fire to a bin? I am probably just being paranoid. I live in a nice area with no antisocial behaviour record, but I am normally with my parents on the 31st. Thankfully, the last couple of years no-one has called, but some children knocked on the door a few years back demanding cash - 'trick or treat' they call. My Dad gave them money - I personally think this was wrong, it is not charity but glorified begging and would normally not be tolerated - I repeat, it is fine with family and friends, but this was not. I have Aspergers, I hate being disturbed, and I am worried some nutter will cause me grief on the 31st. I don't want some stupid sign on my door, so what can I do?