Web console shows a consumer with session but no connection

A destination on a broker was stuck with 108 messages in delivering state. Those messages were to be delivered to a consumer who's connection was closed but the consumer was not. It was still possible to see the consumer with its session in web console. But there was no connection attached to them. This resulted in a situation where the broker had to be restarted due to the fact that there was no way to release those 108 messages.
Calling close on the consumer or its session had no effect.