fix: move NullSymbol declaration inside createSafeContext function

[gwagjiug]

Description

This update resolves an issue with NullSymbol in the createSafeContext function. Previously, a global NullSymbol was used, which could lead to conflicts between different contexts, especially when multiple createSafeContext calls were used. Now, a unique NullSymbol is generated for each context to ensure no conflicts occur.

Changes

• Moved NullSymbol inside the createSafeContext function to ensure each context has its own unique NullSymbol.
• This change eliminates potential collisions between different contexts when createSafeContext is used multiple times.

Motivation and Context

The previous implementation used a shared, global NullSymbol, which could cause conflicts between different contexts, particularly when multiple contexts were created using createSafeContext. By making the NullSymbol unique per context, this change ensures better isolation, preventing potential issues and improving the overall stability of the context system.

How Has This Been Tested?

• Verified that no errors occurred during local testing.

Types of changes

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to change)
• Documentation update

Checklist

• I have performed a self-review of my own code.
• My code is commented, particularly in hard-to-understand areas.
• I have made corresponding changes to the documentation.
• My changes generate no new warnings.
• I have added tests that prove my fix is effective or that my feature works.
• New and existing unit tests pass locally with my changes.
• Any dependent changes have been merged and published in downstream modules.

Further Comments

[changeset-bot]

⚠️ No Changeset found

Latest commit: 801ffe3

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Name	Status	Preview	Comments	Updated (UTC)
overlay-kit	✅ Ready (Inspect)	Visit Preview	💬 Add feedback	Jul 4, 2025 8:07am

[codecov-commenter]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 93.99%. Comparing base (cc91ab2) to head (801ffe3).

Additional details and impacted files

@@           Coverage Diff           @@
##             main     #146   +/-   ##
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  Coverage   93.99%   93.99%           
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  Files          12       12           
  Lines         333      333           
  Branches       80       80           
=======================================
  Hits          313      313           
  Misses         19       19           
  Partials        1        1           

Components	Coverage Δ
overlay-kit	93.99% <100.00%> (ø)

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