Fix porting issue in World.mayPlace Fixes BUKKIT-915

src/main/java/net/minecraft/server/World.java

@@ -2555,7 +2555,7 @@ public class World implements IBlockAccess {
         if (axisalignedbb != null && !this.containsEntity(axisalignedbb)) {
             defaultReturn = false; // CraftBukkit
         } else {
-            if (block == Block.WATER || block == Block.STATIONARY_WATER || block == Block.LAVA || block == Block.STATIONARY_LAVA || block == Block.FIRE || block == Block.SNOW || block == Block.VINE) {
+            if (block != null && (block == Block.WATER || block == Block.STATIONARY_WATER || block == Block.LAVA || block == Block.STATIONARY_LAVA || block == Block.FIRE || block.material.isReplacable())) {
                 block = null;
             }