fix: implicit nullable parameter warning on PHP 8.4

[JoyceBabu]

Fixes

Implicit nullable parameters are deprecated on PHP 8.4.

Resolved by explicitly marking the parameter as nullable. I checked for other instances of this error, but couldn't find any.

Checklist

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• I have made a material change to the repo (functionality, testing, spelling, grammar)
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• I have added tests that prove my fix is effective or that my feature works
• I have added the necessary documentation about the functionality in the appropriate .md file
• I have added inline documentation to the code I modified

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