The Append Routes geoprocessing tool fails and returns the following error, "160145: The field is not nullable.[ASSETTYPE]."

Workaround

1. Use 'Append' to load PipelineLine.
2. Use 'Append' to load LRSnetwork.
3. Author a script to populate the Centerline_Sequence table. The table holds the cardinality or relationship between PipelineLine: LRSnetwork. Reference: LRS data model—ArcGIS Pro | Documentation 
4. Generate Calibration Points or Append Calibration Points.
5. Finally, use 'Generate Routes' to sync up the LRS components.

Steps to Reproduce