Fix: Stopped ships shouldn't block depots #8578
Motivation / Problem
Ships are only allowed to leave a depot when there are no visible ships on the depot tile. This prevents every ship in the depot from leaving simultaneously if the player clicks the green flag to start all ships inside the depot.
Previously, if a ship was stopped immediately after leaving the depot while still on the depot tile, it would block any other ships from leaving the depot.
This changes the depot start check to only consider visible ships which are not stopped. Any stopped vehicles will be ignored, the same as hidden ships.
Checklist for review
Some things are not automated, and forgotten often. This list is a reminder for the reviewers.
I don't know if this is really a problem. Either way, maybe there might be a better solution for providing spacing. I also don't know if my reasoning is correct, but if you replace the limitation of the simultaneous departure of ships by blocking the position (?) with a time block, if possible, it would be good to make the time of the blockade dependent on the speed of the ship that set out and possibly the value that would be defined by newGRF (it is about the length of the ship). As a result, such a solution would provide better spacing between ships. :)