Fix for ClassCastException when attempting to fetch Biome types from BiomeDictionary

Attempting to fetch the BiomeDictionary types linked to a biome throws a ClassCastException. This fixes that
getBiomesForType will cause the same problem
Merge pull request #530 from Azanor/master

Fix for BiomeDictionary.getTypesForBiome throwing a ClassCastException when called.