Fix pack stacking exploit (Sefiraat#73)

Author: Bunnky

src/main/java/dev/sefiraat/cultivation/implementation/listeners/SeedPackListener.java

@@ -38,6 +38,9 @@ public void onPickupItem(@Nonnull EntityPickupItemEvent event) {
         for (ItemStack content : player.getInventory().getContents()) {
             SlimefunItem packItem = SlimefunItem.getByItem(content);
             if (packItem instanceof SeedPack) {
+                if (content.getAmount() != 1) {
+                    return;
+                }
                 ItemMeta contentMeta = content.getItemMeta();
                 SeedPackInstance instance = PersistentDataAPI.get(
                     contentMeta,
@@ -70,5 +73,6 @@ public void onPickupItem(@Nonnull EntityPickupItemEvent event) {
             }
         }
     }
-
 }
+
+