chore: Improve sticker cateId validation in sendSticker

[dinhsan2000]

Updated the validation for sticker.cateId to explicitly check for undefined or null values, ensuring that zero or falsy values are not incorrectly rejected.

What does this PR do?

• This PR updates the validation logic for sticker.cateId to explicitly check for undefined or null values. This ensures that valid values such as 0 or other falsy numbers are no longer incorrectly rejected during validation.

Reason for this PR

• Previously, the validation used a generic falsy check, causing 0—a valid category ID—to be treated as invalid. This led to incorrect validation errors and prevented stickers belonging to category ID 0 from being processed.
• The updated validation improves accuracy and prevents unintended rejections.

How did you verify your code works?

• All related features have been fully tested
• Unit tests have been updated/created if needed
• No lint/format errors
• Documentation has been updated if needed
• Code changes

Related Issue (if any)

• N/A or link to issue here.

Testing Instructions

• Attempt to create or update a sticker with the following cateId values:
• 0 (should be accepted)
• 1 or other valid numbers (should be accepted)
• null or undefined (should be rejected)
• Run the test suite to confirm all unit tests pass.
• Validate that no lint or formatting errors occur during the build process.
• Example payload

{
    "id": 1,
    "cateId": 0,
    "type": 2
}