No errors displayed while loading the project

When DS opens a project, it can display error dialog about missing QML property or file. This happens because runtime starts to render the project despite it has not been loaded yet.

This does not happen 100% but usually it's very often visible with projects with 3D. This is highly annoying.

Fixes to be tried out

• Impact of the new model (with large project)
• loading state of the player (do not render before all assets are loaded)