add_empty_channel = True for derived inputs

Allows derived factory to receive empty channels when requesting input channels. Since input channels are "base" channels, we should allow the underlying timeseries factory to return empty traces if they cannot be found. Otherwise failure will occur when an empty timeseries is passed to the DeltaFAlgorithm or XYZAlgorithm

changed milestone to %Miniseed Pipeline

added Bug label

assigned to @pcain

merged

mentioned in commit 8b89c3a9