Replacing IsNullOrEmpty

[EKAdebo]

Closes #97

This replaces the IsNullOrEmpty method in OpeningType.cs with ((item != null) && item.Any())

[EKAdebo]

@BHoMBot check compliance

[bhombot-ci[bot]]

@EKAdebo to confirm, the following actions are now queued: - check `code-compliance` - check `documentation-compliance` - check `project-compliance` - check `branch-compliance` - check `dataset-compliance` - check `copyright-compliance`

[bhombot-ci[bot]]

FAO: @FraserGreenroyd @EKAdebo 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 branch-compliance. 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. `14477708140`

[FraserGreenroyd]

@BHoMBot this is a DevOps instruction. I am authorising dispensation to be granted on check ref. 14477708140

[bhombot-ci[bot]]

@FraserGreenroyd I have now provided a passing check on reference `14477708140` as requested.

[FraserGreenroyd]

@BHoMBot check core @BHoMBot check serialisation

[bhombot-ci[bot]]

@FraserGreenroyd to confirm, the following actions are now queued: - check `core` - check `serialisation`