handle nulls during cast for like op for ch

[pjain1]

To prevent errors like

Error Message
Code: 349. DB::Exception: Cannot convert NULL value to non-Nullable type: while executing 'FUNCTION CAST(<>: 0, 'TEXT'_String :: 1) -> CAST(<>, 'TEXT'_String) String : 3': While executing MergeTreeSelect(pool: PrefetchedReadPool, algorithm: Thread). (CANNOT_INSERT_NULL_IN_ORDINARY_COLUMN) (version 25.10.1.7375 (official build)) @

Checklist:

• Covered by tests
• Ran it and it works as intended
• Reviewed the diff before requesting a review
• Checked for unhandled edge cases
• Linked the issues it closes
• Checked if the docs need to be updated. If so, create a separate Linear DOCS issue
• Intend to cherry-pick into the release branch
• I'm proud of this work!

[nishantmonu51]

LGTM, Can we add a unit test as well ?

[pjain1]

@nishantmonu51 added test