Fix PHP 8.4 deprecated warning by making $resource parameter explicitly nullable

[mohaelmrabet]

This Pull Request fixes a PHP 8.4 compatibility issue occurring in the Run/Grid/Collection and related grid collection classes.

PHP 8.3+ deprecates implicitly nullable parameters when a parameter defaults to null but is not explicitly typed as nullable.
Magento 2.4.8+ and PHP 8.4+ trigger the following deprecated warning:

Deprecated Functionality: Implicitly marking parameter $resource as nullable is deprecated,
the explicit nullable type must be used instead

This happens because the constructor declares:

\Magento\Framework\Model\ResourceModel\Db\AbstractDb $resource = null

Instead of:

?\Magento\Framework\Model\ResourceModel\Db\AbstractDb $resource = null

What this PR does

• Explicitly marks the $resource and $connection parameters as nullable
• Fixes all affected Grid Collection classes to ensure PHP 8.4 compatibility
• Prevents deprecated warnings when running Magento CLI commands (e.g. bin/magento c:f)
• Aligns with Magento’s strict typing guidelines introduced in recent versions

Why this change is needed

Magento 2.4.x now requires PHP 8.3+ compatibility.
Without this fix, Algolia’s Magento module triggers repeated deprecated notices, particularly on CLI usage and in admin grids.

This PR ensures full compatibility with PHP’s updated typing rules.

Testing

• Tested on Magento 2.4.6-p3 with PHP 8.4
• No deprecated warnings after the fix
• Indexer and admin grids load correctly
• Algolia indexing continues to work as expected

Backward compatibility

• This update is backward-safe:
• Nullable typehints are compatible with older PHP versions
• No breaking changes to public API signatures
• No behavioral changes to the module

[damcou]

Hello @mohaelmrabet and thanks for your contribution !

We will look at it ASAP and it will be added to our next release if it gets approved.
Thanks again !