The Imam should not leave his place of prayer until those behind him complete their prayers, but if he does stand up, there is no blame on him. My father, may Allah سبحانه وتعالى have mercy on him, wrote to me in his letter: If wind or anything else that breaks wudu' comes from you, or you remember that you are not in a state of wudu', then say the Taslim, leave, and appoint someone else to lead the congregation in completing the prayer. Then, perform wudu' and repeat your prayer.