motorcycle-coaster: can build more than one entry and exit

OS: Linux/Gentoo
Version: v0.0.6-HEAD
Commit/Build: 7c7b67f

I wanted to build a motorcycle coaster and was only able to choose 2 vehicles (this is a bug, too, I think). Then I played around with the platform (Stationsplattform), make it longer/shorter, place the entry and exit at other places. Then, when I wanted to test the coaster, an error occurred, saying I have build not entry and exit and the build dialog let me build a second entry and exit. See the screenshots.

• Reproducible in RCT2 (vanilla)?
  Not playable in linux.
• Multiplayer?
  Not tested

Steps to reproduce:
Not sure. I have saved the game, when in the building dialog and builded the first platform. Maybe this is the reason.

Screenshots / Video:

Save game:
First tile of coaster builded: Ivory Towers.txt

Whole coaster but broken: Ivory Towers2.txt

Thank you very much for making RCT available on Linux and keeping it alive!

Start by loading the attached Ivory Towers.txt save files and reproducing the motorcycle coaster build flow in the building dialog on Linux. Check whether the saved first-platform state permits an extra entry and exit, and verify the reported vehicle-selection behavior separately. Done means the unintended second entry/exit can no longer be built and the original scenario behaves consistently.