MinecraftForge/MinecraftForge — pull request #841 by XCompWiz (2013-10-26 10:10:09+00:00)
Title: Adds a Check to prevent Biome Replacement

Adds a check to the BiomeGenBase constructor so that it only puts the
biome object in the biomeList array biomeList[biomeId] is currently
null. This prevents accidental replacement of biomes as well as
allowing biome wrapper objects to exist.