[Bug]: Select values (and JSON input) - unable to convert string timestamps

### Apache Hop version?

2.11.0

### Java version?

17.0.2

### Operating system

Linux

### What happened?

Set up a **Select values** transform in order to convert a `String` in the form `2025-02-13T02:10:14.746582` in a `Timestamp` or `Date` object with format `yyyy-MM-dd'T'HH:mm:ss.SSSXXX`.

When trying to convert it to a `Timestamp`, the error reported is:
```
2025/02/14 11:04:53 - Formato output.0 - ERROR: Unexpected error
2025/02/14 11:04:53 - Formato output.0 - ERROR: java.lang.NullPointerException: Cannot invoke "java.util.Date.getTime()" because "tempDate" is null
2025/02/14 11:04:53 - Formato output.0 - at org.apache.hop.core.row.value.timestamp.SimpleTimestampFormat.parse(SimpleTimestampFormat.java:341)
2025/02/14 11:04:53 - Formato output.0 - at java.base/java.text.DateFormat.parse(DateFormat.java:397)
2025/02/14 11:04:53 - Formato output.0 - at org.apache.hop.core.row.value.timestamp.SimpleTimestampFormat.parse(SimpleTimestampFormat.java:448)
2025/02/14 11:04:53 - Formato output.0 - at org.apache.hop.core.row.value.ValueMetaTimestamp.convertStringToTimestamp(ValueMetaTimestamp.java:262)
2025/02/14 11:04:53 - Formato output.0 - at org.apache.hop.core.row.value.ValueMetaTimestamp.convertData(ValueMetaTimestamp.java:424)
2025/02/14 11:04:53 - Formato output.0 - at org.apache.hop.pipeline.transforms.selectvalues.SelectValues.metadataValues(SelectValues.java:347)
2025/02/14 11:04:53 - Formato output.0 - at org.apache.hop.pipeline.transforms.selectvalues.SelectValues.processRow(SelectValues.java:402)
2025/02/14 11:04:53 - Formato output.0 - at org.apache.hop.pipeline.transform.RunThread.run(RunThread.java:54)
2025/02/14 11:04:53 - Formato output.0 - at java.base/java.lang.Thread.run(Thread.java:833)
```

When trying to convert it into a `Date`, this is the error reported:
```
2025/02/14 11:08:39 - Formato output.0 - ERROR: Unexpected error
2025/02/14 11:08:39 - Formato output.0 - ERROR: org.apache.hop.core.exception.HopConversionException:
2025/02/14 11:08:39 - Formato output.0 -
2025/02/14 11:08:39 - Formato output.0 - create_date String : couldn't convert string [2025-02-13T02:10:14.746582] to a date using format [yyyy-MM-dd'T'HH:mm:ss.SSSXXX] on offset location 26
2025/02/14 11:08:39 - Formato output.0 - 2025-02-13T02:10:14.746582
2025/02/14 11:08:39 - Formato output.0 -
2025/02/14 11:08:39 - Formato output.0 -
2025/02/14 11:08:39 - Formato output.0 - at org.apache.hop.pipeline.transforms.selectvalues.SelectValues.metadataValues(SelectValues.java:353)
2025/02/14 11:08:39 - Formato output.0 - at org.apache.hop.pipeline.transforms.selectvalues.SelectValues.processRow(SelectValues.java:402)
2025/02/14 11:08:39 - Formato output.0 - at org.apache.hop.pipeline.transform.RunThread.run(RunThread.java:54)
2025/02/14 11:08:39 - Formato output.0 - at java.base/java.lang.Thread.run(Thread.java:833)
```

Similar issues happen with the **JSON Input** transform, when trying to read those string timestamps directly as `Timestamp` or `Date`.

### Issue Priority

Priority: 2

### Issue Component

Component: Transforms

Reproduce the conversion through the SelectValues and JSON Input transforms using the sample timestamp and format. Start with org.apache.hop.core.row.value.timestamp.SimpleTimestampFormat and ValueMetaTimestamp, then inspect SelectValues.metadataValues; done means the reported string timestamp conversion behavior is covered and the failing cases are resolved with regression tests.

Written by the indexing model from the issue text.