our dog has had many of these over the years, he is a terrible food thief.
In terms of the wrapper, obviously depends on the size of your dog, but they have never done steppedog any harm, I assume it breaks down a bit as it is paper and then passes through. (steppedog is a springer spaniel)
In terms of the chocolate, it is absolutely fine.
The dangerous thing in chocolate is a specific ingredient, and you can work out how much of that ingredient per kg of dog to see if it is OK.
Let's just say that the year steppedog ate half of dds birthday cake (massive homemade traybake sized thing) there was not even enough cocoa powerd in it to be 1/10 of the amount needed to be dangerous.
The year he ate a whole chocolate orange, was much more of a worry. Again we looked up the amount of grams of cocoa solid (according to the ingredients list) and compared with the weight of the dog.
That was closer. He weighs 20kg. Had he weighed 15, then we might have been in trouble.
He was fine.
Most chocolate is dilute enough that it isn't going to harm them. You need pure chocolate, high percentage to be an issue, (or high volume) cocoa powder in cakes etc just isn't enough.