Fix HTTP 500 bug in user overview

Bug was introduced in commit 3cbc55a0

kraftwerk.py

@@ -661,12 +661,12 @@ if __name__ == "__main__":
 	class ListUsersHandler(BaseHandler):
 		@authenticated
 		def get(self):
-			self.render("users.html", users=[Exercise(**exercise) for exercise in self.db.query("""
+			self.render("users.html", users=self.db.query("""
 					SELECT username, SUM(count) AS count_sum
 					FROM exercises
 					GROUP BY username
 					ORDER BY username ASC, count_sum ASC
-			""")])
+			"""))
 
 	@route(r'/users/(.+)')
 	class ViewUserHandler(ListUsersHandler):