zzz_REBIRTH__Utils/Scripts/Dialog/DialogRequirementHasPlayerBackpackRebirth.cs

public class DialogRequirementHasPlayerBackpackRebirth : BaseDialogRequirement
{
    public override bool CheckRequirement(EntityPlayer player, EntityNPC talkingTo)
    {
        if (player.GetDroppedBackpackPositions().Count == 0)
        {
            return false;
        }

        return true;
    }
}