Hotfix for null reference in ship piloting tutorial

Hey Folks!

Just a quick hotfix (0.15.0.17) here for an issue some players ran into in the new build.

It appears that a null reference could happen if the player uses transit to leave and come back just before the undock step of the tutorial. And this patch fixes that.

We've got some more fixes on the way, but we wanted this one out fast since it can break the new game experience for some.

Best,

Dan