Skip a null tamed owner name when restoring an entity (#1012)

A tamed animal whose owner has no known name is stored with a null owner, and restoring it throws a NullPointerException at the owner step, which drops the rest of the restore. A null owner name is now skipped like an empty one.

src/main/java/net/coreprotect/utility/entity/EntityUtil.java

@@ -195,7 +195,8 @@ public class EntityUtil {
                         }
                         else if (count == 1) {
                             String set = (String) value;
-                            if (set.length() > 0) {
+                            // An owner whose name the server never learned was stored as null
+                            if (set != null && set.length() > 0) {
                                 Player owner = Bukkit.getServer().getPlayer(set);
                                 if (owner == null) {
                                     OfflinePlayer offlinePlayer = Bukkit.getServer().getOfflinePlayer(set);