I do realize this is an old topic, but I have what appears the same problem.
I am using a RuuviTag as hardware and have setup a test website, which points to the Puck.js library. When I test the code from Post #17 I can send the command and I see in the IDE console the date is printed. However in my Chrome Console, I only receive an empty JSON error.
<BLE> Unable to decode "", got SyntaxError: Unexpected end of JSON input
followed by a "null"
I have that problem with all WebBluetooth examples I can find. Any idea how to solve this?