Forge 1865
Minecraft 1.9
Optifine installed
Newest BoP version

Exception in server tick loop

java.lang.IllegalArgumentException: Cannot get property PropertyEnum{name=variant, clazz=class biomesoplenty.common.block.BlockBOPGrass$BOPGrassType, values=[spectral_moss, smoldering, loamy, sandy, silty, origin, overgrown_netherrack, daisy]} as it does not exist in BlockStateContainer{block=minecraft:air, properties=[]}
at net.minecraft.block.state.BlockStateContainer$StateImplementation.func_177229_b(BlockStateContainer.java:192)
at biomesoplenty.common.block.BlockBOPGrass.canSustainPlantType(BlockBOPGrass.java:123)
at biomesoplenty.common.block.BlockBOPGrass.canSustainPlant(BlockBOPGrass.java:164)
at net.minecraft.block.BlockCactus.func_176586_d(BlockCactus.java:114)
at net.minecraft.world.gen.feature.WorldGenCactus.func_180709_b(SourceFile:19)
at rtg.world.biome.realistic.vanilla.RealisticBiomeVanillaMesa.rDecorate(RealisticBiomeVanillaMesa.java:135)
at rtg.world.gen.ChunkProviderRTG.func_185931_b(ChunkProviderRTG.java:601)
at net.minecraft.world.chunk.Chunk.func_186034_a(Chunk.java:996)
at net.minecraft.world.chunk.Chunk.func_186030_a(Chunk.java:979)
at net.minecraftforge.common.chunkio.ChunkIOProvider.callStage2(ChunkIOProvider.java:52)
at net.minecraftforge.common.chunkio.ChunkIOProvider.callStage2(ChunkIOProvider.java:12)
at net.minecraftforge.common.util.AsynchronousExecutor$Task.finish(AsynchronousExecutor.java:188)
at net.minecraftforge.common.util.AsynchronousExecutor$Task.access$800(AsynchronousExecutor.java:73)
at net.minecraftforge.common.util.AsynchronousExecutor.finishActive(AsynchronousExecutor.java:353)
at net.minecraftforge.common.chunkio.ChunkIOExecutor.tick(ChunkIOExecutor.java:30)
at net.minecraft.server.MinecraftServer.func_71190_q(MinecraftServer.java:669)
at net.minecraft.server.MinecraftServer.func_71217_p(MinecraftServer.java:609)
at net.minecraft.server.integrated.IntegratedServer.func_71217_p(IntegratedServer.java:239)
at net.minecraft.server.MinecraftServer.run(MinecraftServer.java:467)
at java.lang.Thread.run(Thread.java:745)

Full crash log and fml-client log are attached.
crash-2016-05-01_15.16.34-server.txt

I have also experienced this. To reproduce, try to place a cactus on a bop sandy-grass block in an Outback Biome. This is a client side only crash.

I to am getting this crash but in 1.8.9 http://pastebin.com/Vd8ZF3Vy difference being i cant load the game without a crash on a brand new world

Similar crash http://pastebin.com/83cuFvfk when loading Mesa Biome. Game crashes repeatedly until player is moved using MCEdit. Seems to only happen with newly loaded chunks. If I go back to the same area later, I can get a little further into the Mesa before it crashes again.
It appears Peach774 and I are both using Realistic Terrain Gen, but Morpheus1101 is not. In all 3 cases it appears another mod is trying to place some kind of plant on a BOP block.

Here's a crash report on a clean install with nothing but forge 12.16.1.1891 and BOP 1.9-4.0.2.2018.
http://pastebin.com/gyA14R24

Steps to produce:

• Placed a Sandy Grass block
• Attempt to place a cactus on the Sandy Grass block. (as Awkanic suggested)

I'm having the same exact issue. Not using RTG.

To play around this, you can disable BoP Soils and BoP Grass under the "customize" setting when creating a new world.

That way you get the BoP worldgen, flowers, tress, etc. That's what I'll be doing until this bug is fixed.

It is a Forge bug. See the comment in #763