It appears that the Camouflage Armor added by the mod Primitive Mobs causes a crash when standing on top of a dynamic cactus. The error looks like this:
-- Head --
Thread: Client thread
Stacktrace:
at com.ferreusveritas.dynamictrees.models.bakedmodels.BakedModelSapling.getModelForSapling(BakedModelSapling.java:43)
at com.ferreusveritas.dynamictrees.models.bakedmodels.BakedModelSapling.func_188616_a(BakedModelSapling.java:92)
at net.daveyx0.multimob.util.ColorUtil.getBlockStateColor(ColorUtil.java:106)
at net.daveyx0.multimob.util.ColorUtil.getBlockStateColor(ColorUtil.java:49)
at net.daveyx0.primitivemobs.item.ItemCamouflageArmor.changeColor(ItemCamouflageArmor.java:191)
at net.daveyx0.primitivemobs.item.ItemCamouflageArmor.onArmorTick(ItemCamouflageArmor.java:54)
at net.minecraft.entity.player.InventoryPlayer.func_70429_k(InventoryPlayer.java:371)
at net.minecraft.entity.player.EntityPlayer.func_70636_d(EntityPlayer.java:511)
at net.minecraft.client.entity.EntityPlayerSP.func_70636_d(EntityPlayerSP.java:1011)
at net.minecraft.entity.EntityLivingBase.func_70071_h_(EntityLivingBase.java:2179)
at net.minecraft.entity.player.EntityPlayer.func_70071_h_(EntityPlayer.java:234)
at net.minecraft.client.entity.EntityPlayerSP.func_70071_h_(EntityPlayerSP.java:181)
at net.minecraft.world.World.func_72866_a(World.java:1996)
at net.minecraft.world.World.func_72870_g(World.java:1958) #

Steps to Reproduce:

1. Install Dynamic Trees and Primitive Mobs
2. Equip Camouflage Armor
3. Plant a cactus seed
4. Stand on top of the cactus seedling