Crash when you place railroad on a mine

[Kriss7475]

How to reproduce:
1. Lauch Map Editor
2. Place a Copper Deposit
3. Place a mine on it (neutral)
4. Try to place railroad
5. Wyrmsun closes

Wyrmsun version: 2.7.3

[Andrettin]

How to reproduce:
1. Lauch Map Editor
2. Place a Copper Deposit
3. Place a mine on it (neutral)
4. Try to place railroad
5. Wyrmsun closes

Wyrmsun version: 2.7.3

Sorry for the delay in answering, I hadn't seen this post before. I've reproduced this issue, and fixed it with the latest commit to Wyrmgus. Thanks for the report!