Schema: Edit Model Info Tab - Add placeholder/empty state value for description and parent model

[zcolah]

Is your feature request related to a problem? Please describe.
Currently if a model does not have a description or a parent model, the table displays nothing in the cell. See reference image. This may make the user feel the data has not loaded.

Solution
If a model does not have a description or a parent model, please display the following text: "None" in Text Disabled color. See Figma design for more information: https://www.figma.com/file/jeRhgXqNsP7Bmd2YoQLA4z/Schema-App?type=design&node-id=2303%3A237260&mode=design&t=GbfNzWvfT04t8E3o-1