item manager: assert item composition access is done from client thread

runelite-client/src/main/java/net/runelite/client/game/ItemManager.java

@@ -204,6 +204,7 @@ public class ItemManager
 	 */
 	public ItemComposition getItemComposition(int itemId)
 	{
+		assert client.isClientThread() : "getItemComposition must be called on client thread";
 		return itemCompositions.getUnchecked(itemId);
 	}