[Spark] Make sure we never get NPE from CDC read (#5261)

#### Which Delta project/connector is this regarding?

- [x] Spark
- [ ] Standalone
- [ ] Flink
- [ ] Kernel
- [ ] Other (fill in here)

## Description

The previous fix for `NullPointerException` in #4489 wasn't enough to
catch all cases: `table_changes('tableName', CAST(null AS INT))` would
still result in NPE. This PR fixes it by wrapping the code in try-catch,
and rethrowing correct error on NPE.

## How was this patch tested?

New unit test with casted null.

## Does this PR introduce _any_ user-facing changes?

No

Add version

Add version

new kernel version

add version

kernel 4.0.1-b951eb11-sharing

bump kernel 8-17-2025

kernel 3.4.0-310dbe5f0-dbi

version upgrade

3.4.0-20250717-1bea60656-dbi