[Bug]: JSON input transform loses the field to read from when it depends on success of a database query

### Apache Hop version?

2.15

### Java version?

OpenJDK 17

### Operating system

Windows

### What happened?

When the field a JSON input transform reads is dependent on the success of a database query, the field vanishes in case the SQL query fails (e.g. due to non-existent table)

See the attached zip and the screenshots.

[HOP-5953.zip](https://github.com/user-attachments/files/23357677/HOP-5953.zip)

### How to reproduce:
- create a simple query in a Table input transform that packs a column (e.g. "id") read from a database into a string in JSON format , stream field that contains the JSON is called "id_json"
- read "id" out of the JSON-string via "JSON Input" transform, under "Select field:" use "id_json" in the drop-down
- as long as the query works / table exists, the JSON input parses everything correctly

- now change the SQL query to use a NON-existing table and save the Table input transform
- edit the JSON input transform: accept both error messages
- what you see afterwards in the "File" tab of the "JSON input" transform is that the "Select field" LOST the field "id_json"

- if you now hit OK and save (accidentally) the pipeline is stored with empty field to read from. (Happened a lot and caused quite a lot of troubles.)

### Issue Priority

Priority: 3

### Issue Component

Component: Hop Gui, Component: Transforms

Start by reproducing the failure using the Table input and JSON Input transforms described in the issue, including a query against a non-existent table. Trace how the failed query affects the JSON Input transform's Select field value; done means the id_json field remains available and is not saved as an empty input after the error messages are accepted.

Written by the indexing model from the issue text.