Fixed asset show page erroring when asset not associated with model

[marcusmoore]

The system encourages assets having an associated model but it is not enforced on the database level.

This PR allows the asset display page to render without 500ing when an asset does not have a model associated.

[what-the-diff]

PR Summary

• Enhanced Interface Rendering
  The display conditions of certain sections on the hardware overview page have been updated. This change ensures that a specific part of the page (the 'model files section') only loads if the asset has an associated model. This update enhances the overall application stability and user experience by removing potential errors when navigating to hardware assets without a model assigned.

• Added System Test
  A new system test has been implemented to confirm the consistent functionality of the hardware overview page. This test checks whether this page correctly presents all the necessary information even when the model of an asset is not provided. Adding this test enhances our software reliability, as it allows us to identify and fix potential problems in this functionality quicker.