API to get a BlockState without a snapshot

This allows you to get a BlockState without creating a snapshot, operating
on the real tile entity.

This is useful for where performance is needed

also Avoid NPE during CraftBlockEntityState load if could not get TE

If Tile Entity was null, correct Sign to return empty lines instead of null

paper-server/src/main/java/org/bukkit/craftbukkit/persistence/CraftPersistentDataContainer.java

@@ -177,4 +177,10 @@ public class CraftPersistentDataContainer implements PersistentDataContainer {
     public String serialize() {
         return CraftNBTTagConfigSerializer.serialize(this.toTagCompound());
     }
+
+    // Paper start
+    public void clear() {
+        this.customDataTags.clear();
+    }
+    // Paper end
 }