Empty JSON being saved to local storage

[cfisher-scottlogic]

Background

Developers at UBS are sometimes experiencing empty JSON is being saved to local storage. It's not actively causing problems, but it could be indicative of problems earlier in the chain (e.g. React -> JSON serialization). We should ensure an empty layout definition does not get saved.

Work Required

• Put (a) guard clause(s) in place to stop saving empty or undefined layouts for both applicationLayout and layout
• Trigger error notificationb when save layout action is executed with empty layout {}

Notes

Related: #115 (comment)