Null reference exception when starting a project which shows the Tutorials window by using the new window docking mechanism.
Don't show Tutorials window when starting a project if there are no tutorials configured to be ran in the project (no `TutorialContainer` asset).
Tutorial not auto-advancing when a tutorial instruction involved exiting Play Mode.
Null reference exception upon returning to a tutorial page with video when the same tutorial page was exited earlier by choosing *Show Tutorials* menu item.
