Nullcheck

[jenspapenhagen]

Linked Issue

Closes #

Description

Type of Change

• Bug fix (non-breaking change that fixes an issue)
• New feature (non-breaking change that adds functionality)
• Breaking change (fix or feature that would cause existing functionality to not work as expected)
• Documentation update
• Refactoring (no functional changes)
• Performance improvement
• Test coverage improvement

Changes Made

SPEC Compliance

• This PR implements/fixes spec compliance
• Spec section(s) affected:
• Spec version:

Testing

• All existing tests pass
• Added new tests for changes
• Tests cover edge cases and spec compliance

Pre-submission Checklist

• My code follows the project's coding standards
• I have run code formatting/linting tools
• I have added tests that prove my fix/feature works
• New and existing tests pass locally
• I have updated documentation if needed
• I have reviewed the TOON specification for relevant sections

Breaking Changes

• No breaking changes
• Breaking changes (describe migration path below)

Additional Context

[github-actions]

Code Coverage

Overall Project	98.33% -0.01%	🍏
Files changed	99.13%	🍏

File	Coverage
DecodeHelper.java	100%	🍏
DecodeContext.java	100%	🍏
JsonNormalizer.java	100%	🍏
ObjectMapperSingleton.java	100%	🍏
Headers.java	100%	🍏
EncodeOptions.java	100%	🍏
DecodeOptions.java	100%	🍏
JToon.java	100%	🍏
ObjectEncoder.java	99.75% -0.25%	❌
StringValidator.java	99.22%	🍏
TabularArrayEncoder.java	98.96%	🍏
HeaderFormatter.java	98.78%	🍏
KeyDecoder.java	98.15%	🍏
PrimitiveEncoder.java	98.11%	🍏
Flatten.java	97.36%	🍏
TabularArrayDecoder.java	97.34%	🍏
ArrayDecoder.java	97.09%	🍏
ValueDecoder.java	95.69%	🍏
ArrayEncoder.java	95.53%	🍏
PrimitiveDecoder.java	94.78%	🍏