Spams "The node was removed from its node repeat sequence" on sequence creation

node_repeat checks on node update to see if the date has changed and removes it from the sequence when it has, but it does this check when the node hasn't been created yet. Of course, if the old date doesn't exist, it tries to remove it from the sequence. Since the node hasn't been created, it doesn't remove it, but it does spam the user with messages saying it has, which is confusing and annoying. This patch just skips the check if the node doesn't exist yet so these messages don't get sent.