[Bug]: Enhanced JSON Output throws unexpected error when group fieldname no longer exists

### Apache Hop version?

2.3

### Java version?

jdk-16.0.1.9

### Operating system

Windows

### What happened?

- create a Data Grid action with field Field1
- connect to Enhanced JSON Output
- define Field1 as Group Key
- run pipeline -> success
- rename field in Data Grid to Field2
- run pipeline, JSON action throws unexpected error

```
2023/03/15 13:56:12 - Enhanced JSON Output.0 - ERROR: Unexpected error
2023/03/15 13:56:12 - Enhanced JSON Output.0 - ERROR: java.lang.IndexOutOfBoundsException: Index: 1, Size: 0
2023/03/15 13:56:12 - Enhanced JSON Output.0 - at java.base/java.util.ArrayList.rangeCheckForAdd(ArrayList.java:756)
2023/03/15 13:56:12 - Enhanced JSON Output.0 - at java.base/java.util.ArrayList.add(ArrayList.java:481)
2023/03/15 13:56:12 - Enhanced JSON Output.0 - at org.apache.hop.core.row.RowMeta.addValueMeta(RowMeta.java:273)
2023/03/15 13:56:12 - Enhanced JSON Output.0 - at org.apache.hop.pipeline.transforms.jsonoutputenhanced.JsonOutput.onFirstRecord(JsonOutput.java:412)
2023/03/15 13:56:12 - Enhanced JSON Output.0 - at org.apache.hop.pipeline.transforms.jsonoutputenhanced.JsonOutput.processRow(JsonOutput.java:118)
2023/03/15 13:56:12 - Enhanced JSON Output.0 - at org.apache.hop.pipeline.transform.RunThread.run(RunThread.java:55)
2023/03/15 13:56:12 - Enhanced JSON Output.0 - at java.base/java.lang.Thread.run(Thread.java:831)
2023/03/15 13:56:12 - Enhanced JSON Output.0 - Finished processing (I=0, O=0, R=1, W=0, U=0, E=1)
```

Not sure if this is a bug and should be captured properly and throwing an error to let the user know that the input field can no longer be found or if its OK to throw an unexpected error instead.

### Issue Priority

Priority: 2

### Issue Component

Component: Actions

Start with the stack-trace locations in JsonOutput.java, especially onFirstRecord, and RowMeta.java at addValueMeta. Reproduce the Data Grid to Enhanced JSON Output pipeline, rename the group field, and determine the intended handling for the missing input field; done means it no longer surfaces as an unexpected IndexOutOfBoundsException.

Written by the indexing model from the issue text.