SPIGOT-4911: Cannot add firework rocket as charged projectile in crossbow

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

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

@@ -141,7 +141,7 @@ public class CraftMetaCrossbow extends CraftMetaItem implements CrossbowMeta {
     @Override
     public void addChargedProjectile(ItemStack item) {
         Preconditions.checkArgument(item != null, "item");
-        Preconditions.checkArgument(CraftMagicNumbers.getItem(item.getType()) instanceof ItemArrow, "Item %s is not an arrow", item);
+        Preconditions.checkArgument(item.getType() == Material.FIREWORK_ROCKET || CraftMagicNumbers.getItem(item.getType()) instanceof ItemArrow, "Item %s is not an arrow or firework rocket", item);
 
         if (chargedProjectiles == null) {
             chargedProjectiles = new ArrayList<>();