Handle null exception when querying unloaded links

[vietle-bh]

Issues addressed by this PR

Closes #1450

I added the null handler.

Test files

Given the PR's scope, code review should be enough?

Changelog

Additional comments

[vietle-bh]

@BHoMBot check required

[bhombot-ci[bot]]

@vietle-bh to confirm, the following actions are now queued: - check `code-compliance` - check `documentation-compliance` - check `project-compliance` - check `core` - check `null-handling` - check `serialisation` - check `versioning` - check `installer`

[bhombot-ci[bot]]

FAO: @FraserGreenroyd @FraserGreenroyd is seeking dispensation on this Pull Request to skip a required check. Please can you provide authorisation for the check to be skipped, or provide assistance as appropriate. The check they wish to have dispensation on is core. If you are providing dispensation on this occasion, please reply with: > @BHoMBot this is a DevOps instruction. I am authorising dispensation to be granted on check ref. `21355996787`

[FraserGreenroyd]

@BHoMBot this is a DevOps instruction. I am authorising dispensation to be granted on check ref. 21355996787

[bhombot-ci[bot]]

@FraserGreenroyd I have now provided a passing check on reference `21355996787` as requested.

[FraserGreenroyd]

@BHoMBot check copyright-compliance @BHoMBot check dataset-compliance

[bhombot-ci[bot]]

@FraserGreenroyd to confirm, the following actions are now queued: - check `copyright-compliance` - check `dataset-compliance`

[vietle-bh]

Thanks @FraserGreenroyd 😉 @BHoMBot check ready-to-merge

[bhombot-ci[bot]]

@vietle-bh to confirm, the following actions are now queued: - check `ready-to-merge`

[bhombot-ci[bot]]

@vietle-bh to confirm, the following actions are now queued: - check `ready-to-merge` There are 2 requests in the queue ahead of you.

[FraserGreenroyd]

Thanks @FraserGreenroyd 😉 @BHoMBot check ready-to-merge

[bhombot-ci[bot]]

@FraserGreenroyd sorry, I didn't understand. Was that comment an instruction for me? If so, could you state again what check you would like me to do? For a list of available instructions, please see [this wiki page](https://github.com/BHoM/documentation/wiki/Continuous-Integration).