Supply BayesWave with a dataseed regardless of whether there is simulated data or not.
Regardless of the type of data (real frames or simulated), BW generates a simulated datastream during its setup (it makes a sim data stream during the checkpoint resume step of real data runs). LAL complains if dataseed isn't provided when generating simulated data: https://git.ligo.org/lscsoft/lalsuite/-/blob/master/lalinference/lib/LALInferenceReadData.c#L829
bayeswave_pipe needs to set up BW jobs such that dataseed is always passed as an argument.