I just joined the Stormcloaks and after a couple of quests I've had dethrone the Jarl of Whiterun, but now continuing with the main story, I have to speak with the old Jarl of Witherun to ask him to catch a dragon there in Whiterun, but of course the Jarl is no longer on the throne because I dethroned a few hours ago so I can not continue with the main mission. What I can do?