Closes #1552

Set the destination block the to the fluid.
In the previous code the destination block was still Air and would would
cause a crash because air doesn't have a property for LEVEL

src/main/java/net/minecraftforge/fluids/BlockFluidClassic.java

@@ -272,7 +272,7 @@ public class BlockFluidClassic extends BlockFluidBase
         if (meta < 0) return;
         if (displaceIfPossible(world, pos))
         {
-            world.setBlockState(pos, world.getBlockState(pos).withProperty(LEVEL, meta), 3);
+            world.setBlockState(pos, this.getBlockState().getBaseState().withProperty(LEVEL, meta), 3);
         }
     }