Fixes NPE when interacting with air

[WalshyDev]

Description

Small bug in the latest change causes an NPE if interacting with air.

Proposed changes

Add a null check before we check for pending deletion.

Related Issues (if applicable)

https://paste.walshy.dev/IwsWtVpt568o

Checklist

• [ ] I have fully tested the proposed changes and promise that they will not break everything into chaos.
• [ ] I have also tested the proposed changes in combination with various popular addons and can confirm my changes do not break them.
• [x] I have made sure that the proposed changes do not break compatibility across the supported Minecraft versions (1.16. - 1.20.).
• [x] I followed the existing code standards and didn't mess up the formatting.
• [x] I did my best to add documentation to any public classes or methods I added.
• [x] I have added Nonnull and Nullable annotations to my methods to indicate their behaviour for null values
• [ ] I added sufficient Unit Tests to cover my code.

[github-actions[bot]]

Your Pull Request was automatically labelled as: "✨ Fix" Thank you for contributing to this project! ❤️

[sonarcloud[bot]]

Quality Gate passed

The SonarCloud Quality Gate passed, but some issues were introduced.

3 New issues
0 Security Hotspots
80.0% Coverage on New Code
0.0% Duplication on New Code

See analysis details on SonarCloud

[github-actions[bot]]

Slimefun preview build

A Slimefun preview build is available for testing! Commit: 34beb766

https://preview-builds.walshy.dev/download/Slimefun/4089/34beb766

Note: This is not a supported build and is only here for the purposes of testing. Do not run this on a live server and do not report bugs anywhere but this PR!