[Bug]: NullPointerException in workflow executor

[liosc]

Apache Hop version?

2.5.0-SNAPSHOT (2023-04-13 07.35.03)

Java version?

11.0.15

Operating system

Windows

What happened?

When a pipeline called by the Workflow executor does not give back any rows, a NullPointerException exception occurs. This happens when in the Workflow executor there is at least one field in the result rows tab.
Here attached an example with:

1. the pipeline using a Workflow executor
2. the workflow called by the pipeline
3. the pipeline called by the workflow
   In the Workflow executor there is a parameter that you can set to have three different scenarios. Here the parameter values and what happens:
   -> 0. The called pipeline gives back a row with the right stream metadata. No errors occur.
   -> 1. The called pipeline gives back no rows. NullPointerException error occurs. In this case the transform should not raise any error
   -> 2. The called pipeline gives back a row but with wrong stream metadata (in this example a missing field). Same NullPointerException error occurs. In this case could be OK to raise an error but it should be handled to have a meaningful message, possibly specifying where the metadata are incongruent (similar to what the GUI highlights when you create a second hop in input to the same transform using different streams).
   wf_executor_nullpointer.zip

Issue Priority

Priority: 1

Issue Component

Component: Transforms