New Jersey’s casinos, horse tracks that accept sports bets, and their online partners won more than half a billion dollars from gamblers in April, an increase of over 10% from a year earlier. But figures released Thursday by state gambling regulators show that was due in large part to the state’s second-best month ever for internet gambling. The industry’s key business — money won from in-person gamblers — continued to sag, down over 6% from a year ago.