easyrtc.call takes five arguments. the fifth is a list of stream names. If that is the empty list, [], then for A calling B, A will not supply any streams.
symmetrically, easyrtc.setAcceptCheck takes a function which in turn is passed a function that takes a list of stream names. If that list is the empty list [], then the called party won’t supply any media streams to the caller.
If you don’t see this behaviour, it would count as a bug.