SPIGOT-7857: Fix spurious internal NBT tag when deserializing BlockStateMeta

By: md_5 <git@md-5.net>

paper-server/src/main/java/org/bukkit/craftbukkit/inventory/CraftMetaBlockState.java

@@ -110,8 +110,10 @@ public class CraftMetaBlockState extends CraftMetaItem implements BlockStateMeta
         } else {
             material = Material.AIR;
         }
-        blockEntityTag = getBlockState(material, internalTag);
-        internalTag = null;
+        if (internalTag != null) {
+            blockEntityTag = getBlockState(material, internalTag);
+            internalTag = null;
+        }
     }
 
     @Override