Output flow on catchments with zero nexus nodes

[mattw-nws]

The latest hydrofabrics do not contain any nexus nodes in some coastal catchments and inland sink catchments. This includes no inflow nexus nodes as well as no outflow! For these catchments, ensure the Q_OUT from the catchment model is copied into the output so that there is some flow output recorded for every catchment.

Current behavior

• Uncertain, but the outflow for these catchments would probably be omitted from the output, as in Output streamflow for catchments with less than 2 nexus #581 .

Expected behavior

• Need output somehow traceable to every catchment, even if it is not "routed"

Steps to replicate behavior (include URLs)

Screenshots